Nancy isn't the only one who's more comfortable hanging about on the fringes of the gathering, although perhaps for different reasons. It's easier for Childermass to catch hold of snippets of conversation this way, easier to spy on the social comings and goings of the other witches if he doesn't have to worry about any social interactings on his part.

That is not to say that he doesn't participate in any conversations at all. He is there when Norrell needs him. And as he spots a familiar face in the crowd, he cannot help but sidle over towards her, even if perhaps she is one of the last people she would care to see there. "I suspect you have seen better days, miss," he remarks to her, offhandedly.