It was on the afternoon of 11 October 1958 that Dimmock first sat behind the desk to anchor a sports show that was to become a constant in the BBC schedules. According to that week's listing in Radio Times, Grandstand was to be 'a new-style, non-stop parade featuring sports and events as they happen, where they happen'. A manifesto to which, 35 years later, the programme still addresses itself.
In 1958, however, it was easier said than done. The show was a technical milestone: the first time several outside broadcasts were linked together in the one programme. Paul Fox, later the BBC's managing director of television, had the idea before anyone really had the know-how to put it into practice.
Dimmock, at the time the executive in charge of outside broadcast, was chosen to front the show because it was felt when things went wrong, he would have the wherewithal to remain unflustered. The opening titles, in which a camera swung round and four sports quartered up its lens, were chosen as a celebration of a technical feat no one was certain would be accomplished.
'In the end, it all worked,' Dimmock remembered. 'The only complete Horlicks we made was when I introduced the Horse of the Year Show and up came pictures from Ascot.'
And so was born a national institution. When it became clear that things were not going to collapse around the ears, Dimmock quickly returned to his back room. And David Coleman, a young sports reporter from the Midlands, was brought in to occupy the hot seat.
He was followed by a succession of smooth front-men, who all made their names as still voices amid confusion: Frank Bough, the incomparable Des Lynam and now Steve Rider. Given how many managers most football clubs have gone through in the same period, the five presenters represent absolutely remarkable continuity.
A continuity, moreover, reinforced by the fact three long marchers involved in the first show - Harry Carpenter, Peter O'Sullevan, and Len Martin - will be there this afternoon. Martin, incidentally, has yet, in 35 years of reading football results, to be faced with the scoreline East Fife 4, Forfar 5.
But the big leap forward for Grandstand came when the technology facilitated the link-man moving out of the studio to present from the main sports event of the day. These are the great Grandstands: Des at Wimbledon, Coleman perched on a windy gantry at the Olympics, Steve Rider at the Cup Final, the Grand National, the Ryder Cup or Twickenham. Then the programme takes the viewer with them, into the heart of sport's big days.
The programme's on-the-spotness has had its tragic tail-spin. They had cameras at Hillsborough and were able to report on disaster as it happened, a facility no one predicted it might need in 1958.
The big-event Grandstands, however, have in recent years put more workaday editions, like the one scheduled for this afternoon, into the shadow. Particularly since rival sports broadcasters have begun to strip its assets. In the old days, even a mundane Saturday would be enlivened by live rugby league, for instance. Now Sky has the contract for the league, Grandstand has to be satisfied with occasional cup games.
Last Saturday, after Football Focus (along with the results service the most-watched section of the programme) came coverage of triathlon from Bath. Despite the democratic attractions of covering minority sports, they remain of, well, minority interest. And the viewing figures reflect it. With Wimbledon and the Five Nations' Championship flirting with other broadcasters, will last Saturday's pattern become the norm?
''I would dispute the term minority sport,' Dave Gordon, Grandstand's editor, said. 'The show's strength has always been its range; we don't cherry pick sports like other broadcasters and in a year will expect to cover 50 sports. A year is a long time in broadcasting, things change. Remember we lost football for a while, but now have it back. Sure we may lose some plums, but look at the contracts we have got.'
The BBC does have long-term involvement with Formula One, the Grand National, the Open, the Boat Race, the Olympics - enough, Gordon insists, to make any year's Grandstand. He may be right. But the prospect of Saturday afternoon without Bill McLaren up-and-undering from Murrayfield or Barry Davies enthusing from Wimbledon will hardly have them dancing in the streets of Shepherd's Bush.
'I've no idea if we'll be here for a 50th anniversary. Who knows if the BBC will be, or even The Independent,' Mr Gordon said. 'But if the BBC is still here then, I can guarantee Grandstand will be.'
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