LONDON (Reuters) - A white Briton who was the subject of a 2011 documentary detailing his conversion to radical Islam was jailed on terrorism charges on Thursday on the strength of evidence gleaned from fragments of deleted text recovered from a laptop.
Richard Dart, 30, who was arrested in July just weeks before last summer's London Olympic Games, discussed attacking Royal Wootton Basset, the town which became known for its repatriation ceremonies for British soldiers killed in Afghanistan and Iraq.
Dart had believed his "silent" conversations with fellow conspirator Imran Mahmood, 22, conducted in his flat by typing on a Microsoft Word document on a laptop and then deleting the text, would keep them safe from detection and surveillance.
But over four months, detectives and a computer forensics expert pieced together fragments of the deleted text which they deciphered from 2,000 pages of computer code.
The text showed they talked about targeting "M15 or M16 heads", a reference to Britain's foreign and domestic spy agencies, as well as the attack on Royal Wootton Bassett.
"This was a prosecution that was based on the most high-tech and sophisticated evidence gathering available," said Mark Topping, specialist counterterrorism lawyer for the Crown Prosecution Service.
Mahmood, Dart, who at one time worked as a security guard at the BBC, and Jahangir Alom, who worked for two years as a Police Community Support Officer, admitted last month to engaging in preparation for terrorism.
The son of teachers from Weymouth, a seaside town in southern England, Dart gained fame when he appeared in the BBC film "My Brother the Islamist" which documented how he had been converted by Anjem Choudary, Britain's most prominent radical Muslim cleric.
He and Alom, 26, travelled to Pakistan in July 2011, after the documentary appeared earlier in the year, in the hope of receiving training from the Taliban or al Qaeda. But they returned a month later having failed in their aim.
They then enlisted the help of fellow Briton Mahmood, who received training in Pakistan. He was detained when he arrived back in Britain when officials found traces of high explosives on his rucksacks, but was not arrested.
Dart was given a six-year prison term and Mahmood was jailed for nine years and nine months.
Alom, who was a part-time soldier but left for medical reasons before joining the police, was jailed for four and a half years.
His wife was jailed for 12 months last December for possessing terrorist material and her brothers were imprisoned in February last year for being part of a plot to bomb the London Stock Exchange. All were also British citizens.
Editing by Sonya Hepinstall