I think he's referring to the closing ceremony at the Olympics, where Boris shambled on, and not quite knowing what he was supposed to do with his hands, shoved one into a pocket. He was rescued by the Mayor of Bejing, who shook his hand, giving him something to do with it.
He wasn't the most sharply dressed of the dignitaries, but this is Boris Johnson we're talking about - he could be dressed by the finest on Saville Row and look as though he'd fallen backwards through a hedge on his way out of the changing room.
To be honest, given the option of a scruffy Johnson or an immaculately (and expensively) suited Livingstone, I think I'd rather go for the former...