A British Muslim convert, who appeared in a BBC documentary, was reportedly one of six people arrested over a suspected terror plot, just over a mile away from the site of the Olympic Games.
Richard Dart, 29, who changed his name to Salahuddin al-Britani, was among those detained in Ealing, west London, on Thursday morning.
Dart appeared in a BBC documentary titled, My Brother The Islamist, in which he spoke of his support for jihad and shaira law and told of how he had been converted by controversial cleric Anjem Choudary.
The six, who include a former police community support officer, were being held at a south east London police station on suspicion of the commission, preparation or instigation of acts of terrorism.
The alleged plan reportedly involved targets in the UK, but was not linked to the Olympics.
The arrests were part of a pre-planned intelligence-led operation by the counter-terror command, but the threat was not thought to be imminent, reported The Sydney Morning Herald.
The arrests come after Jonathan Evans, director-general of the security service, said last month that Britain had experienced a "credible terrorist attack plot about once a year since 9/11".
"In back rooms and in cars and on the streets of this country there is no shortage of individuals talking about wanting to mount terrorist attacks here," he said.
"The threat is real and remains with us today," Evans added.
A neighbor in Stratford said that the three brothers had been “getting more religious throughout the years,” according to The Telegraph.
The threat to the UK from international terrorism is currently rated substantial, which is the third highest of five levels.
The rating is set by the Joint Terrorism Analysis Centre, based at MI5's headquarters at Thames House in central London.