I mean the dude is there to get something done, not bomb the plane. Otherwise id already be dead. So if he doesnt have any intention yo boow the plane unless things go wrong, why not ask for a selfie?
Believe it or not, he wanted to talk to his ex-girlfriend in Cyprus and forced the plane to land there. It was also a fake belt (made out of wrapped phone cases) which people suspected and is presumably why the guy is so relaxed - but they had to follow his demands anyway as a precaution.
Twoflower
Might as well ask, the worst he can do is say no.
Britain has been without conflict for long enough that their natural response to danger has atrophied. A rare but not unheard of phenomenon that is seen is species such as quokka.