Barot scanned hundreds of pages from scientific reference books

The investigation into al-Qaeda plotter Dhiren Barot was unusual for its vast scale and the complexity of the evidence, Scotland Yard has said.

Codenamed Operation Rhyme, it saw 4,000 garages and lock-ups visited and the seizure of nearly 300 computers and around 1,800 items of discs, CDs and removable storage.

The case also involved a wide range of investigative methods, including forensic linguistics, to prove the authorship of documents, facial mapping, computer forensics and handwriting analysis.

He is a full-time terrorist. His training showed through Metropolitan Police Al-Qaeda plotter jailed

Until the 7 July London suicide bombings, it was the largest counter-terrorist investigation launched in the UK.

The Met's counter-terrorism chief, Deputy Assistant Commissioner Peter Clarke, described Barot's arrest and conviction as a "landmark" in the fight against terrorism.

"He is a full-time terrorist. His training showed through. He used anti-surveillance, coded messages and secret meetings, but he could not evade capture," he said.

Mr Clarke added: "For well over two years we have been unable to show the British public the reality of the threat they faced from this man. Now they can see for themselves the full horror of his plans."

Laptop seized

Officers decided to move against him when Barot's terror plans were found on a laptop seized in a raid in Pakistan.

Barot was first identified and put under surveillance in the UK on 15 June 2004.

However, Barot knew counter-surveillance techniques, rarely stayed anywhere for more than a night, used a variety of different vehicles and hardly ever used mobile phones.

He would also perform sudden manoeuvres in heavy traffic or circle roundabouts to make it more difficult to be tailed.

His apparent lack of income led to the assumption that he was being funded by terrorist connections.

Barot, though, disappeared from view by the end of July 2004.

Build case

It was while officers had lost track of him that Barot's plans to use gas cylinders in limousines to cause explosions were uncovered in Pakistan.

Research for the UK plot was found in this west London computer room

Detectives decided they had to arrest Barot as soon as he re-surfaced, and he was identified by a surveillance team in August 2004.

On 3 August he was arrested when he went for a haircut in Willesden High Street, north London.

Officers then had to build a case against him within 14 days' custody time.

One indication of the scale of the task facing detectives was more than 600 sets of keys - officers spent 14 months attempting to match them to garages and lock-ups.

Questions remain

Faced with mounting evidence against him, Barot became the first British Muslim to admit a plot to carry out a mass-casualty terrorist attack in the UK.

Despite such a thorough investigation, some questions about Barot remain unanswered - detectives still have little idea what he was doing in 2002 and 2003, and why he converted to Islam.

He had not had any regular employment, apart from one spell, since he left his job at Air Malta in 1995, and he claimed to have married a woman in Thailand but she has never been traced.