British intelligence complicit in torture

Moazzem Begg, who hwas also a detainee, says that British agents were there at all stages of his detention:
I remember very well when I was held – not just in Guantánamo, but also in Bagram and Kandahar – that British intelligence services were present at every leg of that journey. I knew one of them from the UK because he'd ­visited my house in Birmingham, so we already knew each other when I saw him again at Kandahar and Bagram. It's well-known, especially to all the Guantánamo prisoners, that the British intelligence services were present. The evidence is well-corroborated.