Prosecutors were considering today whether seven men accused of plotting mass murder on board transatlantic aircraft should face a retrial after a jury failed to reach verdicts.
Three of the men were convicted of conspiracy to murder yesterday - but the jurors could not agree over prosecution claims that they intended a wave of suicide bombings on flights from Heathrow Airport to North America.
UK counter-terrorism officials felt it was the strongest case ever brought in a British terror trial and were astonished at the jury's indecision, according to reports.
There were suggestions today that the US may have forced the British authorities to move against the men - who were under surveillance - sooner then they wanted.
In early August 2006 Pakistani security services detained a man allegedly linked to the plot, reportedly at the request of American agencies.
Peter Clarke, the retired head of Scotland Yard's Counter Terrorism Command, said British officials had to act in response to this arrest.
Writing in The Times, he said: "On the evening of August 9, 2006 I was told that a man connected to the British terrorists had been arrested in Pakistan.
"This was not good news. We were at a critical point in building our case against them."
Mr Clarke said Scotland Yard decided "in a matter of minutes" to move against 20 suspects, fearing that they could destroy evidence or panic and mount a "desperate attack".
Conservative MP Patrick Mercer, the former shadow homeland security spokesman, told the BBC's Newsnight: "(The suspect), as I understand it, was arrested at the behest of American agencies in Pakistan at very short notice and without telling the British intelligence agencies, without giving them very much warning of what was going to occur.
"As a result of which, a number of operations against our enemies inside this country were not executed to the level that we would have wished.
"There wasn't as much evidence gathered, for instance, as people wanted.
"And, as a result, I know for a fact that a number of military agencies felt that, with more consultation, they would have been able to get more evidence and that actually a number of their operations came close to being compromised."
He added: "What seemed like a very open-and-shut case clearly is not.
"And it makes me wonder slightly at some of the language that the Home Secretary at the time, John Reid, was using. He was quite sure that this was the plot that was going to go ahead. Well, clearly, a jury is less sure."
The three Islamic extremists convicted of conspiracy to murder - Abdulla Ahmed Ali, 27, Assad Sarwar, 28, and Tanvir Hussain, 27 - are now facing lengthy prison sentences.
They were members of an east London al Qaida-inspired terror cell which planned to detonate home-made bombs in attacks on British targets including Heathrow Airport, the jury at Woolwich Crown Court found.
The three had already admitted planning a series of small-scale headline-grabbing bomb attacks.
But, by a majority of 10 to two, the jurors rejected their claims that they did not plan to kill or hurt anyone in the blasts.
The trial lasted five months and the eight men and four women on the jury deliberated for 56 hours and nine minutes.
But they could not agree verdicts on whether another four Muslim men - Ibrahim Savant, 27, Arafat Waheed Khan, 27, Waheed Zaman, 24, and Umar Islam, 30 - were also involved in the conspiracy to murder.
All seven defendants earlier admitted conspiring to cause a public nuisance by distributing al Qaida-style videos threatening suicide attacks in Britain.
The Crown Prosecution Service (CPS) has until the end of this month to decide whether the men should face retrial.
An eighth man, Mohammed Gulzar, 27, was cleared on all charges.
The trial judge, Mr Justice Calvert-Smith, adjourned the case for sentencing at a later date.
He paid tribute to the jurors' efforts throughout the lengthy trial, describing them as a "unique bunch of 12 people", and released them from future jury service.
The jury found that Ali, Sarwar and Hussain intended to murder people using an ingenious form of hydrogen peroxide liquid bomb disguised as a soft drink.
Prosecutors said his gang considered national infrastructure targets including gas terminals and oil refineries.
Evidence revealed that Canary Wharf, the Bacton gas terminal pipeline, various airports, the electricity grid and internet providers were studied.
Documents also referred to Coryton Oil Refinery in south Essex, Fawley Oil Refinery in Hampshire and Kingsbury Oil Refinery in Warwickshire.
Police said the plot was drawn up in Pakistan with detailed instructions passed to Ali during frequent trips to its lawless border with Afghanistan.
They believe a mystery al Qaida bombmaker is responsible for the ingenious liquid bomb design concealed within 500ml Oasis or Lucozade bottles.
Surveillance teams watched Ali on his return to Britain as he assembled his terror cell, gathered materials and identified targets.
Undercover officers looked on as the unemployed former shop worker used cash to purchase a £138,000 second-floor flat in Forest Road, Walthamstow, east London.
They planted a secret bug which revealed that it was converted into a bomb factory where Ali met the others to construct the bombs.
The flat was also used as a location for Ali and his cell to record suicide videos threatening further attacks against the West.
In his video Ali warned the British public to expect "floods of martyr operations" that would leave body parts scattered in the streets.
On his arrest, Ali was found carrying an elaborate and damning blueprint for the plot scrawled in a battered pocket diary.
Airport security arrangements and details of flights, including the seven highlighted services, were discovered on a computer memory stick in another pocket.
But the jurors could not agree on verdicts on the prosecution's evidence that Ali intended to target passenger jets flying from London to major North American cities with suicide attacks.
In his defence, Ali said he wanted to create an internet documentary protesting against British foreign policy in Iraq, Afghanistan and Lebanon.
He claimed the apparent suicide video, and those created by five of his co-defendants, were spoofs aimed at making the documentary more provocative.
Ali said the blasts would create a storm of media attention which would propel the video into the spotlight.
Home Secretary Jacqui Smith welcomed the conclusion of the trial.
She said: "I am indebted to the police and security services who, by successfully disrupting this group, have saved countless lives.
"I would also thank the Crown Prosecution Service, which has worked tirelessly to ensure that these individuals have been brought to justice.
"I am sure they will now consider what to do where no verdict was reached."
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