It seems it is. This might turn out to be Tony Blair's undoing. Very interesting stuff indeed.
Q&A: Cash for peerages affair Police investigating whether cash has been donated to political parties in exchange for peerages have arrested a fourth person. Here is our guide to the affair.
Who has been arrested?
Downing Street's director of government relations Ruth Turner, a close aide of Tony Blair.
Has she been charged with anything?
No. She has been released on police bail pending further inquiries. She was also questioned by police in September, but not under caution. This time, in addition to being quizzed on suspicion of offences under the Honours (Prevention of Abuses) Act, she was questioned on suspicion of perverting the course of justice. She denies any wrongdoing.
What does this mean for Tony Blair?
Mr Blair was interviewed by police in December but not under caution, which means he was being treated as a witness and not a suspect. But Ms Turner's arrest has been seized on by Labour's opponents as a sign the investigation is moving closer to Mr Blair. The prime minister had previously been assumed to be in the clear. It has also led to further allegations of "sleaze" against Labour.
What is the police inquiry all about?
Scotland Yard is investigating claims that laws made in 1925 banning the sale of honours have been broken by political parties giving peerages in return for donations and loans. They are also investigating whether a law made in 2000 which says that all donations of more than £5,000 must be declared, was breached. All concerned in the inquiry deny wrongdoing. Nobody has been charged.
READ MORE ON WHAT THE LAWS SAY What prompted the investigation?
It emerged last year that a number of large secret loans had been made to the Labour Party before the 2005 General Election, and that some of those lenders had subsequently been nominated for peerages. The investigation has since widened to cover the other main parties.
What has happened so far?
Metropolitan Police Assistant Commissioner John Yates wrote a letter, dated 13 November 2006, saying that "significant and valuable material" had been gathered after 90 people were interviewed. He told Commons public administration committee chairman Tony Wright that he expected to pass a file to the Crown Prosecution Service in January. That date is likely to have slipped a little following the latest developments, the BBC understands.
Who else has been arrested during the inquiry?
Labour chief fundraiser Lord Levy has been arrested and interviewed twice. Biotech boss Sir Christopher Evans, who lent Labour money, was arrested last month. And in April this year, Des Smith, a head teacher who helped find sponsors for the government's flagship city academies programme was arrested and questioned. All of them have denied any wrongdoing.
What's at the heart of the controversy?
Tony Blair has been accused of selling peerages after four businessmen who gave Labour £4.5m in unpublicised loans were subsequently nominated for peerages. Labour went on to reveal it had been secretly loaned nearly £14m ahead of the last election. The Conservatives borrowed £16m from 13 wealthy backers. The Liberal Democrats have said they owe £850,000 to three backers.
What's wrong with people lending parties money?
Nothing, legally. But the suspicion, denied, is that those lending the money are trying to buy influence.
Is anyone else investigating?
The Commons public administration committee has a separate inquiry but it has postponed interviewing key players while the police continue their inquiries.
How did the loans to Labour come to light?
The existence of the loans emerged after the independent watchdog which vets party nominations for new peers raised concerns about some of the men nominated. One of those, Chai Patel, then revealed he had lent Labour £1.5m in 2005.
Who knew about them?
Tony Blair says he did and the party's general secretary did - but Labour's treasurer Jack Dromey and other elected party officials didn't. Mr Blair's fundraising chief and close friend Lord Levy is thought to have arranged the loans.
Didn't Tony Blair promise to clean up politics?
He did. That's what makes the secret loans row so embarrassing for the prime minister - Labour has been caught exploiting a loophole in his own regulations. Rules introduced by him after he came to power in 1997 mean all donations above £5,000 have to be declared and foreign donations are banned. Loans at commercial rates were allowed.
Who lent Labour the money?
The men who lent money and were then nominated for peerages were: Barry Townsley, a stockbroker who has also donated money towards a City Academy School; Sir David Garrard, a property developer who also donated money to a city academy; Dr Chai Patel, chief executive of Priory Clinics. Sir Gulam Noon, who says he was advised to keep a £250,000 loan secret, and that he was blocked from joining the House of Lords once the loan came to the attention of the Lords appointment commission.
FULL LIST OF LABOUR LENDERS What about the Conservatives?
The party has released the 13 names whose loans - worth £16m in total - have not yet been repaid. But it has paid back £5m to lenders - including foreign nationals - who wanted to remain anonymous.
TORY LIST IN FULL And the Liberal Democrats?
The party said it had been lent £850,000 from three supporters. These are trade and industry spokesman Lord Razzall, businessman Paul Marshall and textile millionaire Lord Alliance.
What has happened to the money?
It was spent by the parties on campaigning during the 2005 general election.
Don't party donors always get peerages anyway?
Not automatically, no. Each year the party leaders can nominate a certain number of new peers, which often includes people who have given money to their party. The recent Power Commission report said every Labour donor who had given more than a million pounds had received a knighthood or a peerage.
So how are peers appointed?
Peers nominated by political parties are vetted by the House of Lords Appointments Commission for their propriety, not their suitability. The commission can raise concerns but the prime minister has the final say. It also recommends people for non-party peerages.
That is a new update to a cash for peerage scandal that broke quite a while ago now. I was in the UK when it first broke. I don't think the first peerage scandal effected Blair in the last election, though it may have added to his falling popularity mainly due to Iraq.
Blair aides face charges By Robin Millard in London April 21, 2007 03:21pm
CLOSE allies of British Prime Minister Tony Blair are set to be charged in the "cash for honours" row that has tainted his final year in office, newspapers said today.
Police investigating the allegations on today handed a 216-page file to the Crown Prosecution Service (CPS), which will now decide whether anyone should face criminal proceedings in the case.
The 13-month inquiry was launched amid claims that political parties, mainly Mr Blair's governing Labour Party, had illegally offered their financial supporters seats in parliament's unelected upper House of Lords.
Mr Blair was interviewed twice as a witness in the probe, the first sitting prime minister to be questioned as part of a criminal inquiry, as the police gradually closed in on his Downing Street office.
The Financial Times said Mr Blair "looks almost certain to escape prosecution".
But The Times said it understood that two of Mr Blair's closest allies face charges: Lord Michael Levy, Labour's chief fundraiser and Blair's Middle East envoy, and Ruth Turner, the Downing Street director of government relations.
The pair and two others were arrested in the probe. They, plus biotech tycoon and Labour backer Sir Christopher Evans, remain on bail. All three deny any wrong-doing.
Under the front-page headline "Charge them!'', the Daily Mail said the police demanded that Lord Levy, Ms Turner and Sir Christopher be prosecuted.
The Times said it understood that police had also discussed possible charges against Sir Christopher, Blair's longest-serving aide Jonathan Powell, and John McTernan, the prime minister's political secretary, though it was unclear whether they were recommended for prosecution.
"The evidence under normal circumstances would be considered as strong. But who knows what will happen in this case. The stakes are so incredibly high,'' a source told The Times.
The newspaper said they would have to wait around three months for a decision.
The Financial Times said it understood that any charges would almost certainly be brought after Mr Blair's resignation, expected by many pundits to come in May.
In a statement, London's Metropolitan Police said that 136 people had been questioned either as witnesses or suspects as part of the probe.
Members of Mr Blair's cabinet were among those quizzed.
Iraq deemed too dangerous for Harry May 17, 2007 - 7:02AM
Britain's Prince Harry will not be sent to Iraq as previously planned, the country's army chief said, insisting concerns for his safety had forced the decision.
The 22-year-old prince, third-in-line to the throne, was "very disappointed'' by the announcement but would not quit the army, a royal spokesman said.
General Sir Richard Dannatt acknowledged that Harry would not be pleased with the decision, but said the risk that he and fellow troops would be targeted was too great.
"I have decided today that Prince Harry will not deploy as a troop commander with his squadron,'' he said in a statement, adding that his decision was "final''.
"There have been a number of specific threats - some reported and some not reported - which relate directly to Prince Harry as an individual.
"These threats expose not only him but also those around him to a degree of risk that I now deem unacceptable.''
Harry is a second lieutenant in the elite Blues and Royals regiment of the Household Cavalry.
Dannatt insisted in April that Harry would join the regiment on a six-month tour of duty in Iraq later this month. He was due to be in charge of 11 soldiers and four Scimitar reconnaissance vehicles.
But recent weeks have been some of the bloodiest for the 7,100 British troops in Iraq - 12 died last month alone and a total of 148 have now died there since the March 2003 US-led invasion.
A commander of Iraq's biggest Shiite Muslim militia, Abu Mujtaba, told The Guardian newspaper in April that it had "a special unit that would track (Harry) down, with informants inside the bases''.
Some media reports have suggested that Harry could resign from the army if he was not allowed to go to Iraq.
He himself said in 2005: "There's no way I'm going to put myself through Sandhurst (the army officers' training college) and then sit on my arse back home while my boys are out fighting for their country.''
But Clarence House, the official residence of Prince Charles and his two sons Harry and William, made it clear that he would not quit in the wake of the announcement.
"Prince Harry is very disappointed that he will not be able to go to Iraq with his troops on this deployment as he had hoped,'' it said in a statement.
"He fully understands and accepts General Dannatt's difficult decision and remains committed to his army career.
"Prince Harry's thoughts are with his troops and the rest of the battle group in Iraq.''
Dannatt, who did not rule out Harry, who is known as Cornet Wales in his regiment, deploying to Iraq in the future, acknowledged that he would not be happy.
"Let me also make quite clear that as a professional soldier, Prince Harry will be extremely disappointed,'' he said.
"He has proved himself both at Sandhurst and in command of his troop during their training.
"I commend him for his determination and his undoubted talent - and I do not say that lightly.
"His soldiers will miss his leadership in Iraq, although I know his commanding officer will provide a highly capable substitute.''
Prince William is also an officer in the Blues and Royals, but is unlikely to see frontline military action, given his status as future monarch.
The last British royal to serve in a war zone was William and Harry's uncle, Prince Andrew, who was a Royal Navy helicopter pilot during the 1982 Falklands War.
UK Labour Party anoints Brown Thursday May 17 06:35 AEST
Finance minister Gordon Brown is assured of becoming Britain's next prime minister without a vote after winning overwhelming backing from his party's legislators.
The ruling Labour Party said 307 of the party's 353 lawmakers had nominated Brown to be the party's next leader, which will automatically make him prime minister once Tony Blair steps down at the end of June.
News reports said at least one more Labour legislator would nominate Brown on Thursday and that another, the deputy speaker of parliament, would not nominate anyone.
That made it mathematically impossible for Brown's only possible rival, left-winger John McDonnell, to obtain the 45 nominations he needs to qualify as an official candidate.
McDonnell, who had secured just 29 nominations with less than a day to go before nominations closed, conceded defeat.
"Naturally, I congratulate Gordon and wish him every success in government, but it is a great shame that Labour Party members will now not be allowed a vote on the leader of their party or the party's future direction," he said in a statement.
Since Brown has no challenger, there will be no vote among Labour Party members and the six-week leadership contest becomes a formality.
Brown, who has long nursed an ambition to be prime minister, will have to explain his policies at 10 campaign-style "hustings" around Britain over the next few weeks.
But he is now certain to be proclaimed the party's next leader at a conference on June 24 - three days before Blair resigns after a decade as prime minister.
Many party members had called for an election, rather than a "coronation" of Brown, to allow for a debate on the direction of the Labour Party, which many believe needs fresh impetus after a decade in power.
But, one by one, potential heavyweight challengers ruled themselves out. Five candidates have so far secured enough nominations to take part in an election to be Labour's deputy leader.
Blair won three national elections but his popularity was undermined by his support for the Iraq war and by a series of political scandals and Labour now lags behind the opposition Conservatives in the polls.
The next parliamentary election is not expected until 2009.
Setting out his stall in recent days, Brown has pledged to make education an investment priority and has tried to seize the green initiative by announcing plans to build five environmentally friendly "eco-towns".
He has accepted mistakes were made in Iraq but has ruled out an immediate pullout of British troops.
A video has appeared on the internet showing the first pictures of BBC correspondent Alan Johnston since his abduction in Gaza on 12 March.
It is said to have been posted by the Army of Islam, the group that says it is holding the reporter.
In the video, Mr Johnston says he is in good health and that his captors have treated him well.
The BBC said it was studying the video carefully and repeated its call for the immediate release of Mr Johnston.
Prime Minister Tony Blair, on his visit to South Africa, said Mr Johnston was a journalist of "independence and integrity".
"I feel deeply for Alan Johnston and his family. We are doing everything we possibly can do to secure his release," he said.
[ALAN JOHNSTON PETITION: More than 130,000 people have written to the BBC to demand Alan Johnston's release]
Chancellor Gordon Brown called on those holding the reporter to free him "as a matter of urgency" as they were "not serving their cause by detaining him in this unfair and unjust way".
In a statement, the Foreign Office said: "We condemn the release of videos like this, which can only add to the distress of Alan Johnston's family and friends."
A statement released by Mr Johnston's family in Scotland said relatives were "very pleased to see Alan and to hear him say that he is not being ill-treated - although it is clearly distressing for us to see him in these circumstances".
Mr Johnston, 45, was seized nearly 12 weeks ago in Gaza City on his way home.
It is unclear when the video, which has appeared on the al-Ekhlaas website, was recorded.
Nor was it clear under what conditions the Scottish reporter was speaking.
On the video Mr Johnston says: "First of all, my captors have treated me very well... They have fed me well, there has been no violence towards me at all and I'm in good health."
Mr Johnston, seated and wearing a red sweatshirt, calls for an end to Western sanctions that have been imposed on the Palestinian government.
[ARMY OF ISLAM FACTS Small, Islamist armed group operating in Gaza Splinter group of the Popular Resistance Committees Seeks liberation of Palestine and an Islamic state Influenced by, but not affiliated with, al-Qaeda Led by Mumtaz Dugmush, also known as Abu Muhammad, a member of a powerful clan. One of three groups allegedly holding captured Israeli soldier Cpl Gilad Shalit]
Video: Full transcript
Mr Johnston talks of the "huge suffering" of the Palestinian people, saying: "Everyday there are Palestinians arrested, imprisoned for no reason. People are killed on a daily basis. The economic suffering is terrible, especially here in Gaza."
He also says the British government is working to occupy Muslim lands against the will of the people there.
Mr Johnston refers to the "failed invasion of Iraq by America and Britain" and the "terrible" situation in Afghanistan.
Towards the end of his portion of the video, Mr Johnston begins a message to his family, saying, "to my family, to my family..." but the audio is then cut off.
A message then appears on screen in English saying: "BBC refused to take this message to his family". The BBC's Bridget Kendall says it appears that the kidnappers added this to the video.
In response the BBC said it had kept the family informed throughout and the Johnston family statement said relatives had been "fully informed and involved by the BBC since the day Alan was abducted".
The BBC statement read: "This is a highly distressing time for them and for his friends and his colleagues. We repeat our call for his immediate release."
On the tape, the Army of Islam demand the release of Abu Qatada, a Palestinian-born Islamic cleric who is suspected of close links to al-Qaeda and is currently held by the UK government as a threat to national security.
Senior Palestinian negotiator Saeb Erekat again called for the unconditional and immediate release of Mr Johnston and said that all Palestinians stood behind him.
Mr Johnston was the only Western reporter permanently based in Gaza and his abduction has triggered appeals for his release from lawmakers and rights groups around the world.
More than 130,000 people have now signed an online petition calling for his release.
Father orders daughter's brutal death June 12, 2007 - 11:26AM
A father who ordered his daughter's brutal death for falling in love with the wrong man in a so-called honour killing has been found guilty of murder in the UK.
Banaz Mahmod, 20, was strangled with a boot lace, stuffed into a suitcase and buried in a back garden.
Her death is the latest in an increasing trend of such killings in Britain, home to some 1.8 million Muslims. More than 100 homicides are under investigation for being potential "honour killings".
Mahmod Mahmod, 52, and his brother Ari Mahmod, 51, planned the killing during a family meeting, prosecutors told the court.
Two others have pleaded guilty in the case. Two more have fled the country. Sentencing is expected this month.
The men accused the young woman of shaming her family by ending an abusive arranged marriage, becoming too westernised and falling in love with a man who did not come from their Iraqi village. The Kurdish family came to Britain in 1998 when Banaz Mahmod was just 11.
"She was my present, my future, my hope," said Rahmat Suleimani, 29, Banaz Mahmod's boyfriend.
More than 25 women in Britain have been killed by their Muslim relatives in the past decade for offences they believe have brought shame on their family. More than 100 other homicides are under investigation for potential honour killings.
Some Muslim communities in Britain practice Sharia law, or strict Islamic law.
"We're seeing an increase around the world, due in part to the rise in Islamic fundamentalism," said Diana Nammi with the London-based Iranian and Kurdish Women's Rights Organisation.
During the three-month trial over Banaz Mahmod's murder, prosecutors said the girl's father began beating her at an early age for using hairspray and becoming too westernised.
Her uncle once told her that she would already have been "turned to ashes" if she were his daughter and had shamed the family by becoming involved with the Iranian Kurd, her sister 22-year-old Bekhal Mahmod testified.
Banaz Mahmod ran away from home when she was a teenager, but was later sent an audio tape in which her father warned he would kill her sisters, her mother and himself if she did not come home, her sister said.
She returned home and was later hospitalised after her brother attacked her, her sister testified. The brother said he had been paid by their father to finish her off, but in the end was unable to do it, the sister said, testifying in a full black burqa. She said she still feared for her life.
The years of Banaz Mahmod's abuse were compounded by officers who repeatedly dismissed her cries for help.
She first went to police in December 2005 when she suspected her uncle was trying to kill her and her boyfriend. She sent the police a letter naming the men who she thought would later kill her.
On New Year's Eve, she was lured by her father to her grandmother's home and believed she would be attacked after he forced her to gulp down brandy and approached her while wearing gloves. She escaped by breaking a window, and was treated at a hospital.
Police dismissed her claims. One officer, who is under investigation, considered charging her with damages for breaking her grandmother's window.
Laying in her hospital bed after the escape, Banaz Mahmod recorded a dramatic video message saying she was "really scared".
The videotape, taken by her boyfriend at the hospital, was shown to the jury during the trial. The boyfriend feared it could be the only chance she would have to detail her fears.
After she was released from the hospital, she returned home and tried to convince her family she stopped seeing her boyfriend, according to court documents.
But friends told the family they spotted the couple together on January 22, 2006.
Soon after, a group of men allegedly approached her boyfriend and tried to lure him into a car but he refused. It was that event that prompted Banaz Mahmod to go to police again. This time officers tried to persuade her to stay in a safe house. She refused, believing her mother would protect her, according to court documents.
But her mother and father left her alone in the house the next day. Her boyfriend - who noted the absence of text messages - quickly alerted police.
Her body was not discovered until three months later, after police tracked phone records.
One of the men who fled the country is allegedly the man who arranged for her burial in the northern city of Birmingham.
Blair appointed as Middle East peacemaker By Washington Correspondent Michael Rowland and wires
Mr Blair's appointment as the new special envoy for the Middle East negotiating Quartet was announced just hours after he formally resigned as Britain's prime minister.
He will work towards a Middle East peace settlement on behalf of the European Union, Russia, the United States and the United Nations.
In a statement, the Quartet said Mr Blair would mobilise aid for the Palestinians, seek to build their governing institutions and promote economic development.
Mr Blair, 54, replaces former World Bank president James Wolfensohn, who resigned in April of last year in frustration at the difficulty of making progress on a problem that has defied diplomacy for nearly 60 years.
The Quartet praised Mr Blair, British premier for 10 years, for having "long demonstrated his commitment on these issues" and said he would "bring continuity and intensity of focus to the work of the Quartet in support of the Palestinians."
"He will spend significant time in the region working ... to help create viable and lasting government institutions representing all Palestinians, a robust economy, and a climate of law and order for the Palestinian people," it said.
But some European diplomats have raised questions about Mr Blair's ability to garner broad Palestinian and Arab public support because of his role in the US-led 2003 invasion of Iraq and his close ties with President George W Bush.
12 killed in Gaza
Meanwhile Israeli forces killed at least 12 Palestinians, mostly gunmen but also a 12-year-old boy and other civilians, in the deadliest raid in the Gaza Strip since Hamas seized the territory, medical workers said.
Israel's operation in Gaza City and the southern town of Khan Younis appeared to signal it intended to keep strong military pressure on Hamas along with efforts to isolate the movement financially and politically.
The announcement of Mr Blair's appointment was made by UN spokeswoman Michele Montas.
"Following discussions among the principles, today the quartet dealing with the Middle East is announcing the appointment of Tony Blair as the quartet representative," she said.
"Mr Blair has long demonstrated his commitment on this issue. Tony Blair will be supported in this work by a small team of experts based in Jerusalem to be seconded by partner countries and institutions."
Announcing that he was retiring from Parliament to take up his new role, Mr Blair spoke of what he hoped to achieve.
"The absolute priority is to try to give effect to what is now the consensus across the international community that the only way of bringing stability and peace to the Middle East is a two-state solution," he said.
"Which means a state of Israel which is secure and confident of its security and a Palestinian state that is not only viable in terms of its territory but also in terms of its institutions and governments."
Mr Blair faces a formidable task, with Israeli-Palestinian talks stalled for seven years against a background of the rise of Hamas, a string of Palestinian suicide bombings and rocket attacks against Israel, and harsh Israeli reprisals.
An aide for Palestinian President Mahmoud Abbas, Nabil Abu Rdainah, said the Palestinian president "hopes (Mr Blair) can help relieve the suffering of our people and provide basic needs".
The Palestinian Hamas Islamist movement, shunned by the United States and its European allies after winning elections 18 months ago, sought to cast Mr Blair as an ally of Israel.
"We do not expect Blair's role to be fair in any issue relating to the Palestinian-Israeli conflict or any other Arab-related cause," Hamas official Ghazi Hamad said.
Mr Blair himself has acknowledged the difficulties of a peace-making role meant to steer the Palestinians towards statehood after Hamas' violent takeover of the Gaza Strip.
The United States was quick to welcome the appointment.
"I am pleased that this capable man has agreed to continue his work for peace in the Middle East," Mr Bush said in a statement.
But White House spokesman Tony Snow also sought to play down expectations.
"Tony Blair is not the person who comes in and says, 'A-ha, I will solve it'," he said.
"He's not Superman. He doesn't have a cape."
Rumours that Mr Blair would get the job had gathered pace for several days, with Russia, which has quarrelled with Britain over a spy controversy in the past year, the last of the quartet partners to give its assent.
Second London car bomb found June 29, 2007 06:04am
BRITISH police have found a second car bomb near Park Lane in central London after defusing a similar device packed with nails outside a city-centre nightclub. A senior police officer said the two bombs were "clearly linked."
The Metropolitan Police anti-terrorism chief Peter Clarke said the second vehicle, a blue Mercedes which was taken to a car pound after being discovered near the first one, contained similar material to the first, including nails.
"These vehicles are clearly linked,'' he told reporters, adding that the development was "obviously troubling.''
The presence of a second car bomb was confirmed after police earlier today sealed off London's Park Lane and Fleet St as they investigated other suspicious vehicles following the discovery of the first bomb.
The first bomb was found in a green Mercedes parked outside a nightclub shortly after 1am London time, when hundreds of people were packed in the busy night-life district a kilometre from the Prime Minister's Downing St residence.
The police, alerted by ambulance workers who thought they saw smoke inside the car, defused the bomb, which Sky News said was rigged to detonate with a mobile-phone-triggered device.
Authorities said they did not know who left the bomb but they had begun a counter-terrorism investigation.
“It is obvious that if the device had detonated there could have been significant injury or loss of life,” Peter Clarke, the head of London's anti-terrorist police, said.
He said there were similarities between today's incident and an earlier plot, uncovered in 2004, in which an al-Qaeda militant planned to detonate gas-fuelled bombs inside limousines in London, among other targets.
It might also have echoes of another recent plot to attack targets including a high-profile nightclub, Mr Clarke said.
Prime Minister Gordon Brown, facing a major challenge two days after succeeding Tony Blair, convened Britain's top security committee, Cobra.
“We are currently facing the most serious and sustained threat to our security from international terrorism,” Jacqui Smith, Mr Brown's new interior minister, said after the meeting.
A large area of central London around the scene remained sealed off hours after the bomb was found.
Television pictures showed a gas canister after it had been removed from the car.
It was green and labelled “PATIO GAS”, which is readily available at hardware stores in Britain.
Explosives officers also found “significant quantities” of petrol and a large number of nails in the car, Clarke said.
Britain has experienced an increase in terrorism-related threats since the September 11 attacks on the US and since it joined forces with US troops to invade Iraq in 2003, an event that provoked widespread domestic criticism.
Mr Brown has pledged to respect Britain's commitments in Iraq, although there has been speculation he may accelerate the British troop withdrawal.
The alerts followed a series of coordinated suicide bomb attacks on London's transport network two years ago which killed 52 commuters, the first Islamist suicide bombings in western Europe. London has frequently been on edge since then.
Intelligence sources said they could not rule out an al-Qaeda link to the car bomb, and said the danger of international Islamist terrorism was the main reason Britain's threat level is placed at “severe”, the second highest rating.
“We're following up lots of leads and hopefully making some progress, but we're still keeping quite an open mind,” a security source said.
“The balance of probability does lie pretty strongly with international terrorism,” the official said, referring to al-Qaeda-inspired radical Islamism.
But the source added: “Until we feel that we know who's responsible, we're not going to start pointing the finger.”
Mr Brown said the incident showed the need for vigilance.
“The first duty of a Government is the security of the people and as the police and security services have said on so many occasions, we face a serious and continued security threat to our country,” he said.
Security around Parliament was stepped up, with police body-searching drivers of vehicles entering the compound.
Car bomb: The race for evidence By Dominic Casciani BBC News home affairs
The car bomb found in central London on Friday morning is being taken to a specialist maximum security laboratory. The Forensic Explosives Laboratory has experts on around-the-clock stand-by to deal with terrorist incidents.
Once a device such as a car bomb is made safe, it is taken to the small team based in a complex hidden away in the Kent countryside.
The scientists painstakingly examine car bombs in the specialist "X47" laboratory built during the IRA era.
The X47 building complex most recently housed the remains of the bus blown apart by one of the 7 July 2005 London suicide bombers.
The Forensic Explosives Laboratory and its 60 staff deal with the remains of bombs - or unexploded bombs used against the UK or British interests, such as UK forces abroad.
While the 130-year-old laboratory is an arm of the Ministry of Defence, much of its work is with police forces, dealing with all types of incidents from reckless garden-shed experimenters through to the attacks on 7 July 2005.
The small team of scientists are hand-picked through a specialist recruitment programme. It take up to four years to build up the expertise needed to become a qualified case officer capable of identifying bombs from their remains or chemical signatures.
While details of their work remains secret, many of their conclusions become public when the investigators take to the witness stand as experts in prosecutions.
Once police have sealed a suspected bomb incident scene, the Forensic Explosive Laboratory's scientists, working with bomb disposal experts, assess the risks to the public and themselves posed by the device, particularly if it has not exploded.
Once scientists are sure that they can safely move a device or the remains, bomb disposal experts prepare it for the journey to the specialist laboratory.
Where a bomb has detonated, such as in the IRA's attacks on the capital, the critical issue is the search for remains of the bomb and clues towards the identity of those behind the device.
This can lead to literally thousands of boxes of rubble being taken to the laboratories. Once there, special machinery is used to first sort the rubble into different sizes before it is carefully dried out.
The scientists then essentially have two priorities - to establish the facts about the bomb and to uncover details critical for the police operation.
Different teams look for different things. Some scientists look for mechanical elements - such as remains of wires or timing devices.
Experts can spend weeks, if not months, sifting through box upon box of debris - usually with nothing more than a pair of tweezers.
Just one small piece of wire, tape or plastic may be a critical lead if police can link it to a suspect.
Others will look for the chemical "characteristics" of a device. These tell-tale chemical traces may again provide all-important evidence that allows the police to link a bombing to a suspect or a "bomb factory".
These procedures also help the scientists to build a chemical portrait of the bomb - meaning that it could be linked to previous explosions.
A third line of inquiry is to look for DNA or other evidence, such as clothes fibres, left on the device by the bomb-builder.
Wimbledon police chiefs have altered their security plan for the championships following today's defusing of a car bomb in the heart of London.
Superintendent Peter Dobson, in charge of the police operation at the All England Club, said that, while there had been no specific threat to Wimbledon, security measures at the Championships had been fine-tuned in the wake of the incident.
"Whilst I have made some adjustments to the security of the perimeter, with some police officers being redeployed from inside, and some enhanced checking of vehicles entering the car parks, the security plan remains commensurate to the threat," Dobson said.
"There is no intelligence that increases the threat to the championships. My message is for all persons attending to remain vilgilant and to report anything suspicious to the police.
"This is a timely reminder that we live in dangerous times and our top priority will always remain the safety of the public."
The new plan means more vehicle interiors are being checked and there is a higher police presence around the egde of the club, which is bordered by busy roads, a golf course and suburban housing.
Amid widespread disruption in city, new Prime Minister Gordon Brown warned that the alert was a fresh warning of the threat faced by Britain, which soon marks the second anniversary of the London suicide attacks which killed 52 people.
Since the July 7, 2005 bombings, Wimbledon has brought in airport-style searching with tennis-watchers having to pass through metal detectors and bag checks.
The queues of fans who camp out overnight to get tickets - a traditional Wimbledon feature - were moved away from the site's perimeter to reduce the possibility of a direct attack.
And vetting procedures were also strengthened in a bid to thwart bogus applicants for accreditation passes.
Police said 19 people had been arrested in the first four days of this year's championships, for offences ranging from the possession of offensive weapons to cannabis possession, disorder, indecent assault, theft, fraud and immigration-related offences.
Dobson said people had tried to bring knives, tear gas canisters and pepper sprays into Wimbledon this year.
"If people bring illegal items to the club they will be dealt with robustly, and that usually means arrest and prosecution," he said.
Ladies' singles top seed Justine Henin said she was not worried by the bomb scare. "Everyone heard about that," the world number one said. "But I feel quite safe here."
A chronology of some of the worst bomb attacks on mainland Britain in the past 30 years.
February 1974 - Coach carrying soldiers and families in northern England bombed by the Irish Republican Army (IRA). Twelve people killed, 14 hurt.
October-November 1974 - Wave of IRA bombs in British pubs kills 28 people and wounds more than 200.
July 1982 - Two IRA bomb attacks on soldiers in London's royal parks kill 11 people and wound 50.
December 1983 - IRA bomb at London's Harrods department store kills six.
October 1984 - Prime Minister Margaret Thatcher's cabinet narrowly escapes IRA bomb which kills five people at Brighton hotel during the Conservative Party's annual conference.
December 1988 - A Pan Am Boeing 747 crashes on the town of Lockerbie, Scotland, killing all 259 aboard after a bomb on board explodes. Eleven people in Lockerbie are also killed.
September 1989 - Bomb at Royal Marines Music School in Deal, southeast England, kills 11 and wounds 22.
February 1991 - The IRA fires mortar bomb at Prime Minister John Major's London office. No one is injured.
April 1992 - Huge car bomb outside Baltic Exchange in London's financial district kills three people and wounds 91.
March 1993 - Bombs in two litter bins in Warrington kill two boys aged three and 12.
April 1993 - IRA truck bomb devastates Bishopsgate area of London's financial district, killing one and wounding 44.
February 1996 - Two people die when IRA guerrillas detonate large bomb in London's Docklands area.
March 2001 - A powerful car bomb explodes outside the BBC's London headquarters. Police say the Real IRA, a republican splinter group opposed to the IRA's ceasefire, was behind the blast. One man was wounded.
July 7, 2005 - Four suicide bomb blasts on London transport during the morning rush hour kill 52 people and injure about 700 in the first Islamist suicide bombings in western Europe.
July 21 - British police say four men attempted to carry out a second wave of attacks on three London Underground stations and one bus.
June 29, 2007 - Police defuse a bomb in an abandoned car in the Haymarket, a busy street in the tourist heart of central London.
Would-be London bomber filmed leaving car: reports
Anti-terrorism police in London are making progress in the investigation into a double car bomb attack that has been foiled in the city's west end.
The first bomb, containing petrol, gas canisters and nails was discovered by ambulance officers Tiger Tiger night club in Haymarket.
A second, similar bomb was found several hours later in a car at Park Lane car park in central London.
The second car had initially been parked near the first, but was impounded at the car park for illegal parking.
Both bombs were defused.
Since the first bomb was found, a team of specially trained police officers have been looking at hours of closed circuit TV footage.
Reports, unconfirmed so far, suggest police may have an image of a suspect leaving the vehicle.
Security sources say they think the attacks are the work of Islamic extremists linked to Al Qaeda.
Defence analyst Dr Martin Navias, an expert in biological and chemical capability at Kings College in London, says investigators will be looking at whether the devices are used by insurgents in Iraq.
"One of the most important things that the security services will be trying to determine while they pull apart this car is whether there are any linkages in terms of manufacture between how this car was prepared to be exploded and cars of a similar type in Iraq," he said.
Police patrols are being stepped up and today there will be another meeting of the Government's emergency response committee, COBRA.
The UK's national terrorism threat has been raised to its highest level after an attack on Glasgow Airport was linked to two car bombs found in London.
Two men were arrested after ramming a burning car into the airport's main terminal, a day after police thwarted two attempted bombings in the capital.
Police said one of the men wore a "suspect device" and the incident was being treated as terror related.
Prime Minister Gordon Brown urged the public to remain vigilant.
"I know the British people will stand together, united and resolute," he added.
Strathclyde Police told a news conference the attack on Glasgow Airport was now being linked to the car-bomb plot in London - foiled by police on Friday.
Chief Constable Willie Rae said: "There are clearly similarities, and we can confirm that this is being treated as a terrorist incident."
Two men were arrested at the scene at 1515 BST after the blazing car was driven into the airport's main terminal.
One of the suspects taken to the city's Royal Alexandra Hospital to be treated for severe burns was in possession of "a suspect device" which had been found on his person, Chief Constable Rae said.
BBC security correspondent Frank Gardner said the suspect device was thought to be a "suicide belt".
The second man was being detained in police custody while the vehicle was said to be too unstable to be removed from the airport.
Eyewitnesses described a Jeep Cherokee being driven at speed towards the main doors of Glasgow airport's terminal building with flames coming out from underneath shortly after 1500 BST.
All flights to and from Glasgow Airport have been suspended.
A number of other airports have stepped up security, including Edinburgh, Newcastle, Birmingham, Manchester and Blackpool. John Lennon Airport in Liverpool has been closed as a precaution.
Security has also been tightened at airports across the US following the attempted attacks.
The national terrorism threat level was raised after a meeting of the government emergencies committee, Cobra.
Ministers, police and security service officials held their third meeting of Cobra in recent days on Saturday evening, this time with a video link to ministers in Scotland.
TERROR THREAT LEVELS Low - an attack is unlikely Moderate - an attack is possible but not likely Substantial - strong possibility of an attack Severe - an attack is highly likely Critical - an attack is expected imminently
In a televised statement, Mr Brown thanked the police, the security and emergency services for the "dedicated professionalism" that has been shown in London and Glasgow Airport.
The first duty of the government is the security and safety of all the British people, so it is right to raise the level of security at airports and in crowded places in the light of the heightened threat," he said.
The critical threat level indicates terrorist attacks are imminent. It is the highest possible level and was also in place after the 7 July 2005 suicide bomb attacks on London.
Petrol and gas
A Scottish government spokesperson said Scottish Ministers were in touch with their Whitehall opposite numbers and First Minister Alex Salmond and have spoken to Mr Brown.
Mr Salmond and Justice Secretary Kenny MacAskill took part in the Cobra meeting.
Mr Salmond echoed the prime minister's calls for vigilance.
"We cannot and must not live our lives in a state of alarm but alert individuals have a substantial role to play in supporting our police services," he added.
Earlier in the day, Cobra met to discuss the London car bomb attempts.
In the early hours of Friday, two Mercedes containing petrol, gas cylinders and nails were found left outside the Tiger Tiger club in Haymarket and a nearby street but the devices did not detonate
Police in the capital are checking CCTV footage in their investigation into the planting of the two car bombs.
Unconfirmed reports suggest police may have an image of a suspect leaving the vehicle left outside the Tiger Tiger club.
Police increased patrols and security for events in London over the weekend, including the Gay Pride parade, the Concert for Diana at Wembley Stadium and the Wimbledon tennis championships.