Launched in September 1972, the cerebral quiz has become as much a part of Britain's popular culture as Coronation Street. But the BBC said yesterday that the show was drawing to the end of its natural life. "Although the programme is looking as fresh and vital as ever, and is attracting a wide range of contestants - from punk rockers to vicars - no programme lasts forever," said John Whiston, head of youth and entertainment features for BBC Television.
The BBC is working on plans for a documentary to mark the passing of the series, and a "spectacular final". New ideas are being developed for shows "to take the tradition of Mastermind forward for the future".
Much of Mastermind's success was due to its unflappably grave host, Magnusson, who was occasionally forced to stop the clock when he stumbled over a particularly abstruse pronunciation.
The Icelandic-born presenter, who is writing a book of memoirs, was knighted in 1989 but cannot use his title, because he is not British.
He was consulted about the decision and agreed with it, the BBC said. "Every good thing has to come to an end - and I would rather it ended with a bang than a whimper. We will be retiring from the scene when we are still on the crest, and I shall treat this last series as a celebration," the presenter commented.
In fact, Mastermind had fallen from a high of 20 million viewers in its early years in a prime-time slot. As interest waned, it was moved to Monday nights, where it was watched by fewer than 6 million earlier this year.
But it has been a touchstone for some of the social changes since the early 1970s, not least the huge growth of interest in trivia, which has made fortunes for those who cashed in on the fascination.
The second-longest running quiz on television - second only to A Question of Sport - its format was created by Bill Wright, a prisoner of war in Germany, to echo the inquisitorial atmosphere in the camps. His main prop was the black chair, in which contestants nervously awaited rapid-fire questions on general knowledge or a special topic of their choice. These have ranged from British poisoners to punk rock and beekeeping.
The sinister title music was also devised to induce the tension of a Nazi war camp. Entitled "Approaching Menace" by Neil Richardson, it was commissioned to create a mood of impending doom.
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Mastermind questions answered
The highest total score (41) was achieved by Kevin Ashman in 1995. His specialist subjects were Martin Luther King and civil rights movement, the history of the Western film and the Zulu war
The chair is the original one, used from the first series. It is a hybrid of two commercially available (in 1972) chairs
Of the 23 winners, 16 are men and 7 are women
Taxi driver Fred Housego, Tube driver Christopher Hughes and hospital driver Ian Meadows were winners between 1980 and 1985
Subjects suggested for specialised questions, but not accepted, include: orthopaedic bone cement in total hip replacement, iron graveslabs of England and cremation practice and law
Magnusson, who has never missed a show, says it has little educational valueReuse content