From UK Labour MEP Richard Corbett's blog:
"Am I the only one to think that Boris Johnson's performance at the closing ceremony for the Olympics was an embarrassment? In a solemn part of the ceremony - the handing over of the Olympic flag from the Mayor of Beijing to the Mayor of London, where all the other dignatories involved were, at that point, solemnly walking in a line with their hands by their sides - Boris, uniquely, was periodically waving to the crowd (without much response) as if he was the star of the show. Unlike the other representatives, he (alone) did not even button up his jacket. He never knew what to do with his hands (hence his periodic incongruous waving), and altogether gave the appearance of a buffoon."
Yes, buffoon is precisely the word I was searching for.