I'm Sorry I Haven't a Clue down opportunities to work on it as he preferred to remain a listener. The official, authorised history of the show and ISIRTA, "The Clue Bible" by Jem Roberts, was published by Preface Publishing in October 2009. Humphrey Lyttelton, primarily known as a jazz trumpeter and bandleader, was invited to be chairman because of the role played by improvisation in both comedy and jazz music. In the first series Lyttelton shared the role of chairman with Barry Cryer but he made it his own (especially once Cryer replaced Cleese as a regular panellist) and continued as chairman until his death on
I'm Sorry I Haven't a Clue regular feature on the programme, preceding the game Mornington Crescent, is a fictional letters section which begins with the chairman's comments ("I notice from the sheer weight of this week's postbag, we've received a little over no letters" and "I see from the number of letters raining down on us this week that the Scrabble factory has exploded again"). The invariably single letter each week is from "A Mrs Trellis of North Wales", one of the many prompts for a cheer from the audience, whose incoherent letters usually mistake the chairman for another Radio 4 presenter or media personality. "Dear