"This was the least we could do for you and for Libya to demonstrate the remarkable relationship we have built over recent years," the letter, from Mark Allen, head of counter-terrorism at MI6, said.
"I am so glad. I was grateful to you for helping the officer we sent out last week." The documents, found by Human Rights Watch and circulated at the weekend, show the extraordinarily close relationship that developed between Libyan intelligence and MI6 and the CIA.
The letters show that the CIA arranged the final delivery of both Mr Belhadj and his deputy, known by his nom de guerre of Abu Munthir, with their wives to Libya, but that in both cases Britain provided the original intelligence tip-off.MI6's letters, many written by Mr Allen, now Sir Mark Allen and an adviser to BP, are much more personal in tone that the CIA's, however.