And what was the reason the British government faced this court case? Why, the ex-Guantanamo inmates claimed British complicity with torture. Not that the British committed torture, but that they were complicit with it. They claim that the UK fed information and questions to their interrogators, or gave information to the CIA so it could arrest British suspects overseas where they were tortured.
What was the torture to which they were subjected in Guantanamo and elsewhere? Well, there are a lot of claims but nothing, other than in three cases overall at Guantanamo, has ever been convincingly proved to be anything other than claims made by terrorist suspects. Those three were water-boarded. Read more.