Certainly I can't verify this story as true but it is similar to the Czech Atta story when the Bush Admin. released information passed on by the Czechs who did not want it released.
I think the Brits have the same concern, like their refusal to turn over the African uranium evidence. They fear a mole or a leaker leaking for domestic p.r. or spin control. American government give up secrets for quickie brownie points in the press? I'd believe it.