I spoke to one of the aforementioned friends again this evening and Capaldi came up in conversation. My friend said that there were quite a few people there waiting for autographs, and Capaldi's attitude was basically "I can't believe that all these people want to talk to me". I don't want to put him on a pedestal (that never ends well) but everything I've heard about him suggests that he is an exceptionally decent human being.
...and a very humble one at that, so it seems!
Unbelievable that he can 'morph' into the foul mouthed Malcolm Tucker! Perhaps he's his naughty alter ego who gets to 'escape' when he's acting!