I didn't say he shouldn't be put on trial if the evidence justifies it, which it appears to. But there is no reason to think that an American court is going to be in a better position to carry out such a trial. Any evidence which can be produced in an American court can equally well be produced in a British court.

I rather assume that there are aspects of this which we don't know about, which may explain why there has been no such trial so far. For example, it could well be that there are felt to be advantages from an intelligence gathering point of view having him around. Perhaps he is even a double agent...