My guest in this week's Book Club is Joel Morris, an award-winning comedy writer whose credits run from co-creating Philomena Cunk to writing gags for Viz and punching up the script for Paddington 2. In his new book Be Funny Or Die, he sets out to analyse how and why comedy works. He tells me why there are only three keys on the clown keyboard, what laughter does for us in neurological terms, and why Laurel and Hardy could get away with anything.