This eleven-minute interview with Abu Nusaybah, acquaintance of one of the attackers, is a stark contrast with this week's bloody killing of a British soldier on a London sidewalk.
Woolwich attack: MI5 'offered job to suspect'MI5 asked Woolwich murder suspect Michael
Adebolajo if he wanted to work for them about six months before the killing, a childhood friend has said.
Abu Nusaybah told BBC Newsnight his friend - one of two men arrested after Drummer Lee Rigby's murder in south-east London on Wednesday - had rejected the approach from the security service.
The BBC could not obtain any confirmation from Whitehall sources. Abu Nusaybah was arrested at the BBC after giving the interview.
Newsnight reporter Richard Watson said after the interview had concluded he left the studio to find officers from the Metropolitan Police counter terrorism unit waiting to arrest Abu Nusaybah.
The Met confirmed a 31-year-old man had been arrested at 21:30 BST on Friday in relation to suspected terrorism offences and search warrants were being executed at two homes in east London.
The arrest was not directly related to the murder of Drummer Rigby, it said.
The soldier was killed in front of dozens of people near Woolwich Barracks, where he was based, on Wednesday afternoon.
Mr Adebolajo and Michael Adebowale, who was also arrested at the scene, remain in hospital after being shot by police.'Bugging me'
In his Newsnight interview, Abu Nusaybah said he thought "a change" had taken place in his friend after his detention by security forces on a trip to Kenya last year. Abu Nusaybah said Mr Adebolajo suggested he had been physically and sexually abused during an interrogation in a prison cell in the African country.
After this, he became withdrawn "and less talkative - he wasn't his bubbly self", Abu Nusaybah added. He said Mr Adebolajo also told him that, upon his return, he was "followed up by MI5" who were "knocking on his door"
He was "basically being harassed", Abu Nusaybah said.
He added: "His wording was, 'They are bugging me - they won't leave me alone.' He mentioned initially they wanted to ask him if he knew certain individuals. But after him saying that he didn't know these individuals, what he said was they asked him if he would be interested in working for them. He was explicit in that he refused to work for them but he did confirm he didn't know the individuals."
Reporter Richard Watson said that, in general terms, it was not out of the ordinary for the security service to approach people for information or even to act as covert sources.
Mr Adebolajo, 28, originally from Romford, east London, and fellow suspect Michael Adebowale, 22, of Greenwich, south-east London, had been known to MI5 for eight years, Whitehall sources told the BBC on Thursday.
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