The BBC has been given unprecedented access to one of the founder members of al-Qaeda in the Arabian Peninsula, the group that claimed responsibility for the failed attack on the plane over Detroit on Christmas Day.

Mohammed al-Awfi is a former Guantanamo detainee who was repatriated to Saudi Arabia two years ago. Following an attempt to rehabilitate him al-Awfi defected to Yemen and helped establish the new group.

He alleges that he was tortured while in the custody of the Americans at Bagram Airbase in Afghanistan.

Peter Taylor went to meet him in Riyadh's top security prison to ask about the allegations of abuse and why he thought the Saudi rehabilitation programme had failed.

Peter Taylor's full film for Newsnight will be broadcast on Wednesday 13 January 2010 at 10.30pm on BBC Two or watch again on the BBC iPlayer .