Walker, who is married with three children, describes his OCD as “like a hundred little blackmails a day. You are constantly striking deals with yourself. They can be very minimal blackmails: I’m a keen fisherman and, when I’m getting my fishing tackle out of the box, I will think, 'If I don’t put it back that way, I won’t catch any fish today.’ Then there’s medium-level threats, where if I don’t do things a certain way something bad will happen to me personally – so if I don’t switch the light on and off four times, the press will turn on me. And then there’s what I call 'Defcon 3’, which is, 'If you don’t do that, someone you love is going to be wiped out.’ ” Sometimes it comes out of nowhere, he says. “I’m looking at a picture of my son and the OCD says, 'If you don’t tear this picture up, he will die.’ ”