Actor who punched Mark - hard, "in that way they teach you in public school, with your knuckle sticking out" for being rude about Ikea Knightley.
At the time, Cumberbatch was appearing as a character actor in The Other Boleyn Girl. During his discussion with Simon Mayo, Cumberbatch explained that most of his scenes involved him being naked in bed with Scarlett Johansson. "Is it a small part?" Simon asked. Given his nudity, Cumberbatch bridled at the implications of answering this - and so Simon instead tried, "how extensive is your role?"
Cumberbatch is somewhat more famous now.