Gabriel, having just had a confrontation with Peter" is on his way over to the refreshment table to get something that he hasn't dreamed up himself (preferably alcoholic) when he spots the TARDIS. Any other time, he might have just stayed out of her way out of respect, but right now he's not feeling particularly charitable to her wishes.

As he reaches out for one of the drinks in front of her, he says a rather terse sounding "excuse me" that comes across more as a command than a request.