I think he does it because he loves taking risks--I imagine the conspirator isn't too chuffed about it (unless he is as reckless as Foley), but once Foley's pulled up, there's nothing he can do.

Well, we can agree to differ on that one. I think it's a marvellous contribution to the oblique sense of foreboding in the early part of the book, however you read it: and (as I discovered when I tried to explain it to someone who hadn't read the book) quite sophisticated in narrative terms: Selby's perceptions of Foley's behaviour filtered through Peter's account and then through Nicola's point of view.