Writing comic novels is no laughing matter, and going straight can be even tougher. Phil Rickman negotiates the minefield of mirth with Guy Bellamy, author of The Nudists, A Village Called Sin and The Mystery of Men, whose humour usually springs from personal diaster. Simon Brett, creator of After Henry and the Charles Paris comedy thrillers who's lately been producing thrills without comedy, and Sue Limb, author of Up the Garden Path whose latest novel Passion Fruit deals with the less laughable issue of C18th slavery.