Puns have a long history in human writing. Most of us recognise them as those little gems of comedy genius that make you laugh, or groan, but they're useful for being more than just funny, they're also fundamental to what makes poetry work and they provide the engine of change in language by allowing ideas to slip from one meaning to another. Artist and composer Hannah Catherine Jones, comedy writer Jack Bernhardt, poet Nasser Hussain and Sam Leith - Literary editor of The Spectator - join Ian Macmillan to reveal the linguistic power of the pun.