White Muslim convert Richard Dart and a former police community support officer were among six people arrested for allegedly plotting a terror attack in Britain.
Richard Dart, who was radicalised by the cleric Anjem Choudary, was held following police raids in east and west London.
A former PCSO and two of his brothers, who were living just over a mile from the Olympic site in Stratford, were also among those detained during the police and MI5 operation to prevent a suspected terror assault.
One of the brothers was Tasered by officers. Counter-terrorism police had first searched their home last November.
The Daily Telegraph understands the police moved over fears that a group had obtained a sword which could potentially be used in a terrorist attack.
Mr Dart, 29, the son of Dorset teachers, featured in a BBC documentary last year filmed by his own brother about his conversion. During the film, called My Brother the Islamist, he was seen protesting about British soldiers in Afghanistan and accused them of being “murderers”.
He also called for Sharia law to be established in Britain, as well as saying that one of his friends used to be “in the police”, but is not any more. Mr Dart has changed his name to Salahuddin al Britani. Salahuddin comes from the medieval leader who drove King Richard I from Jerusalem during the Crusades.
It emerged last year that the former BBC security guard was living off state benefits in a luxury flat in Mile End, east London.
Anjem Choudary said he had converted Mr Dart but had not been in contact with him for more than a year.