Andy Capp. Beau is my own creation so it comes more naturally to me. Also, I write weekly themes for Beau (and Horace) and I find it's easier to come up with gags when there's a bit of continuity. I've had to alter my style quite a bit with Andy Capp and the gags are all "one-offs". I write, say, a strip where Andy's in the pub and then I have to start from scratch again with a different setting. It's MUCH harder.
