One of the alleged July 21 bombers was a "fanatical, radical" Muslim who spoke about jihad and listened to speeches by Osama bin Laden, a former friend told a court.
Muktar Said Ibrahim, 29, would apparently discuss fighting those who were against jihad, including the British, Americans and Russians.
The alleged terrorist also watched numerous jihadi films, showing "martyrs" reading their wills and people dying, Woolwich Crown Court heard.
Ibrahim also listened to speeches by the al Qaida leader bin Laden and the extremist Islamic preacher Abu Hamza, the jury was told.
The evidence against the alleged terror plotter came from a friend who lived with Ibrahim for three months at the end of 2004.
Known only under his alibi of Michael Bexhill, the witness gave evidence hidden from the view of the defendants, members of the public and the media.
Instead of sitting in the normal witness box, Mr Bexhill sat at a table to the left of the jury. Large blue screens in front of the dock prevented him being seen by any of the defendants.
Ibrahim, of Stoke Newington, north London, and five others are accused of carrying out an extremist Muslim plot to cause chaos on London's public transport system.
Speaking at times through an interpreter, Mr Bexhill said the jihadi films showed people in Afghanistan fighting the Russians as well as jihad in Bosnia.
In addition, he said, Ibrahim used to listen to recordings of scholars who encouraged people to fight for jihad.
