A former head of Britain's domestic spy agency has accused the US of concealing its abuse of terror suspects, stepping up an MI5 fightback over accusations that it colluded in torture.
Eliza Manningham-Buller said Tuesday she had not understood why alleged 9/11 mastermind Khalid Sheikh Mohammed had been willing to talk to American interrogators.
She said she only discovered he had been waterboarded when she read about it after her retirement in 2007.
"The Americans were very keen that people like us did not discover what they were doing," she said in a specially arranged lecture at Britain's upper house of parliament in London.
The US had been "very keen to conceal from us what was happening."
Her comments come as the spy agency hits back at claims it colluded with US counterparts in the torture of terror suspects.
The allegations were sparked by a British court's decision last month to release details of US torture of a former Guantanamo Bay inmate.
Ex-prisoner Binyam Mohamed -- who was born in Ethiopia but is a British resident -- has charged he was asked questions by US interrogators that could only have come from the British intelligence services.