knife to BBC's management structure

In his programme, Sir David has explored the BBC archive for clips of the great sketch show performers from wartime radio show It's That Man Again and Variety stars such as Ken "Daft as a Brush" Platt to the Two Ronnies, Morecambe and Wise and Bruce Forsyth.He acknowledged that audience nostalgia for historic television was threatened by the wave of allegations against former entertainment stars, including Jimmy Savile and Stuart Hall. "It's unbelievable," he said. "Obviously any one of these terrible incidents where people were assaulted is one too many but I don't know whether we are talking of something more widespread than the people who have been singled out so far. It's that question between whether it is a small group of people or if it is wider."Speaking in the study of his London offices, surrounded by photographs taken with world leaders including Bill Clinton and Mikhail Gorbachev, Sir David also talked of his continuing plans for interviewing world figures for the Al Jazeera English network, for which he has worked since 2006.

A new series of "The Frost Interview", beginning in July, will see him speaking to spaceman Buzz Aldrin, Bangladeshi Prime Minister Sheikh Hasina and racing driver Lewis Hamilton.At 74, he retains his appetite – "as much as ever" - for such encounters. "I could never understand how people could want to retire," he said. But there is one world leader at the top of his interview wish list: Robert Mugabe.In a typical aside, he mentioned how the comedian Bob Monkhouse had alerted him to the fact that "Mugabe spelt backwards is e-ba-gum".Though Sir David spoke briefly with the Zimbabwean leader at a Commonwealth summit in 1991, he has never subjected him to the Frost treatment, with its mixture of easy charm and strategic interrogation. "He has lived longer as leader than anyone thought was possible," he said.