A man named in court as a facilitator of terrorism in the UK is living freely in England, the BBC can reveal.
Mohammed Qayum Khan: named in court
Evidence in the trial of five men jailed for a homemade bomb plot alleged some were working for a senior figure with links to al-Qaeda.
In the unprecedented fertiliser bomb trial, the jury heard a Luton-based man played a key role in sending a 7 July suicide bomber for military training.
Counter-terrorism chiefs have refused to discuss the man, codenamed "Q".
WHO IS Q?
Real name Mohammed Qayum Khan
Based in Luton
Allegedly acted as "facilitator"
Allegedly sent London suicide bomber to Pakistan
Q refused BBC interview requests
Told a newspaper he had been a charity worker
Watched by MI5 in 2003
Police refuse to discuss him
On Monday five men were jailed for life for a 2003-04 plot to build a massive bomb out of fertiliser to use on a target in southern England.
In a record-breaking year-long trial, the Old Bailey heard that the plot's key figures trained with Mujahideen figures in Pakistan. The ringleader of the plot, Omar Khyam, had personal contacts with a senior Al Qaeda figure, now in Guantanamo Bay.
But evidence in the trial also pointed to links between the fertiliser bomb plotters, the 7/7 suicide bombers and a Luton man called Mohammed Qayum Khan.
A part-time taxi driver, Qayum Khan is alleged to have direct links to al-Qaeda figures as part of a broad international "jihadi" network established to facilitate support for causes including the Taleban and Kashmiri separatists.
According to evidence in the trial, MI5 officers discovered the fertiliser bomb plotters after seeing ringleader Omar Khyam in secret meetings with "Q". The last of these was in Southall in west London, shortly before police arrested the plotters.
Suicide bomber: Sent to Pakistan by Q, according to evidence
During the trial it was alleged that Q was a senior inspiring figure for the fertiliser bomb plotters, linking them with military trainers in the Pakistani and Afghan mujahideen.
It was also alleged that he organised fund raising in the UK to send cash to the Taleban or other jihadi groups.
But Qayum Khan, it was also alleged, sent London suicide bomber Mohammad Sidique Khan to Pakistan in July 2003 - a trip which saw him join paramilitary training with other British extremists.
In the trial, it was alleged that Q was a key rallying figure for a growing band of Islamist extremists in the wake of the 9/11 attacks as Luton emerged as a secret powerbase for "jihadi" ideology and activism.
Two Luton men who died in fighting in Afghanistan after the 2001 al-Qaeda attacks on the US lived in the same road as Q.
The taxi driver is also alleged to have had strong ties with another of the jailed fertiliser bomb plotters. Salahuddin Amin, who was living in Pakistan at the time of his arrest, acted as a reciprocal facilitator, receiving money, men and equipment and sending them on to Mujahideen, al-Qaeda or Taleban groups.
Requests for interviews
BBC teams have approached Mohammed Qayum Khan on more than one occasion for an interview or response to the allegations made against him in court.
The BBC's Newsnight team were forcibly thrown out of a cafe in the town centre after identifying Q as eating there and approaching him for comment.
He appears to be no longer living at his home address after approaches from the BBC's Panorama programme.
The Daily Telegraph has also approached Q for an interview. He told the newspaper he knew Omar Khyam and Mohammad Sidique Khan - but only through attempts to raise money for poor people in Pakistan.
Deputy Assistant Commissioner Peter Clarke of the Metropolitan Police refused to discuss Q when asked about his role in the fertiliser bomb plot or in alleged wider jihadi activity.
"I know who 'Q' is but I'm not going to discuss who he is or what he is, or what he does," said DAC Clarke.
"Decisions are made during the course of investigation based upon the evidence that's available, and the decision as to who should be arrested based entirely upon what evidence is available at the time."