The other day the BBC reported on the video evidence given by Saajid Badat in a current US terrorism trial:http://www.bbc.co.uk/news/uk-17821854

It is the first time a convicted UK terrorist has entered into an agreement with the Crown Prosecution Service (CPS) to give evidence in a trial against other alleged terrorists....Prosecutors earlier said Badat's "main motivation" in helping had been to prove he had renounced terrorism with actions as well as words....He saw himself and others like him as victims manipulated and exploited by Bin Laden and Khalid Sheikh Mohammed, they said.
This has now been followed up in this wide ranging article:http://www.telegraph.co.uk/news/ukne...upergrass.html

Which ends with:
...we should not idealise such figures, nor ignore the injustices that reliance on the honesty of criminals and terrorists sometimes entails. But supergrasses do afford a glimpse into the moral squalor of terrorist organisations, while their existence will surely shake the confidence of al-Qaeda cells and their operations. That is something in itself.