What is the real name of the title character in Keith Waterhouse's 1959 novel Billy Liar?

Billy Liar is a 1959 novel by Keith Waterhouse, which was later adapted into a play, a film, a musical and a TV series. The work has inspired and featured in a number of popular songs.

This semi-comical story is about William Fisher, a working-class 19-year-old living with parents Alice and Geoffrey, and his grandmother, Florence Boothroyd. Billy lies compulsively to everyone he comes across, whether it's the claim that his father is a retired naval captain/cobbler, or telling his parents that Arthur's mother has broken her leg. Billy works as a clerk for undertakers Shadrack & Duxbury. He is engaged to two girlfriends, and in love with a third and constantly refers to a vague job offer writing scripts in London for "Danny Boon", a comedian.