The Brits won't take some of the Gitmo prisoners Obama wants to send their way. Can't send them back to Chad, etc., because they might be abused in their home states. Can't keep 'em here, because he has pretty much made that whole Kumbayah thing a major part of his plan as President. And he seemed to think that the Europeans would just jump at the chance to help him out.
Britain and the European countries want some kinda proof that these guys aren't going to be dangerous to them, before they take them in. Which, yeah, is one of those things a lot of Americans want, too. Maybe Obama and friends shouldn't have worked so hard to convince everyone that Bush was holding decent, freedom-loving Muslims at Guantanamo Bay just for shits and giggles.
As Bugs Bunny would say, "It is to laugh."