Roy McKelvie, the self-described "Gruff old silvery lion" who presides over press accreditation for the Wimbledon tennis championships was sitting at center court. An assistant brought him a message: "There's a man in the office wanting credentials. He has just arrived from the Sudan Express."

Without taking his eyes off the match he was watching, McKelvie responded. "Tell him," he said disdainfully, "to take the next express back to the Sudan."

This exchange occurred several years ago, McKelvie, 65 this friday, has mellowed somewhat, but yesterday he was recounting gleefully the list of those whose applications to cover the centenary Wimbledon he had rejected.

"Free-lance applications get no consideration. I turned out 35 provincial British newspapers, which are a flaming nuisance," he began.

"I refused eight newspapers from India, 10 from Germany, 10 from Scandinavia, five from Eastern Europe, seven from Australia, four from South Africa, 15 from Israel, Turkey and the Middle East, 16 from South America and a list from Mexico as long as your arm.

"These are reasonable newspapers I'm talking about, not oods and sods," he said. "The photographers, magazines and frivolous applications must bring the number well over 220."

But despite McKelvie's thorough and sometimes hostile screening due to limited facilities - "We could give away 10,000 seats a day to the press, but we need some for the public, you know" - enough journalists are accredited to make Wimbledon the most extensively covered annual sporting event in the world.

Only the quadrennial Olympic Games and the World Cup soccer tournament exceed it in international coverage.

So far this fortnight, McKelvie has issued 138 center-court badges (access to all press facilities), 41 No. 1 court badges, 50 single-day tickets each day to the center and No. 1 court press boxes, 276 rover passes, and 160 messenger passes.

It is virtually impossible to be in London during Wimbledon and not know that something special is happening at the All England Lawn Tennis and Croquet Club in S.W. 19.

All of Britain's fiercely competitive national newspapers are fuel of match reports, gossip social notes and photographs. Moreover, the noncommercial British Broadcasting Corp. televises matches from 1:50 to 7:30 p.m. every day, with only brief interruptions for news of earth-shaking importance. For most of the day, there is dual coverage on its two channels, center-court matches shown on BBC-1 and No. 1-court action on BBC-2.

BBC radio broadcasts from Wimbledon from 2 until 7 p.m. daily, 1:30 p.m. until 7 on Saturday. "At 4:30, there is a 15-minute break for a sacrosanet serial called 'Wagoner's walk,'" said Max Robertson, a play-by-play commentator at every Wimbledon since World War II. "That's annoying when you're in the middle of a good match, but I think we bridge the break quite well."

The thought of stroke-by-stroke commentary of tennis on radio bewilders Americans who have rarely heard it done well, but Robertson and his colleagues are quick and knowledgeable enough to describe the action graphically and dramatically.

The players in Robertson's broadcasts are hardly expressionless figures hitting forehands and backhands. Between points, they may "stand in the forecourt, arms akimbo, glowering." Some have been known to "look rather like Oliver's Heathcliff."

There is, curiously, a great rivalry between the BBC radio and television crews covering Wimbledon.

BBC telecasts of Wimbledon have improved steadily since, in 1937, the first transmissions carried 25 minutes of a center-court match between Bunny Austin And G. L. Rogers to 2,000 TV sets.

The BBC village behind the north end of the center court is a massive collection of huts, offices, workshops, mobile units and temporary studios.

Three mobile color units, videotape recording vans, a two-story studio/office complex and 12 miles of cable keep complex and 12 miles of cable keep Wimbledon pictures on the air. Some 130 members of technical and production staffs are occupied more than 12 hours a day for the fortnight.

Since BBC technicians and directors are so experienced, their equipment so sophisticated and the two arenas at Wimbledon so visually and acoustically pleasing, the television coverage here is magnificent.

Watching tennis on the BBC, you feel part of the match. You can hear what the players are saying to the umpire. You can hear the crowd practically as the players hear it. And since there are no commercials, you can see the players close-up at change games, when the psychological shifts are so often etched on their faces.

One of the great joys of Wimbledon is sitting down at the breakfast table with toasted scones or a full English breakfast (ham, egg and tomato grill) and poring over stacks of newspapers loaded with the big stories and tasty little tidbits of the previous day's play.

In the morning tabloids - the Daily Mirror, the Sun, the Daily Mail and the Daily Express - Wimbledon is often front and back-page news, with bold, black headlines. The juiciest, most sensational stories of center-court rows and tea room romances appear here often lavishly emblished.

But even the more "serious" journals - the Times, the Guardian and the Daily Telegraph - known as "the heavies" in London - put summaries and photos of Wimbledon action on Page One.

Inside are literate accounts that are often as memorable as the matches they describe.

Who, for example, could forget David Gray, then tennis correspondent of the Guardian and now general secretary of the International Lawn Tennis Federation, likening Margaret Courts epic 14-12, 11-9 victory over Billie Jean King in the 1970 final to "one of those 990-page novels Trollope and Arnold Bennet used to write. It started slowly, but after all the subtle shifts in plot and characterization, it became a matter of utter compulsion to find out how it all ended."

Or his comparison of Jimmy Connors' explosive shotmaking on a good day to "Hemingway's description of artillery: 'You see the flash, then you hear the crack and at least the shell comes.'"

David Irvine, Gray's successor felt the pressure of filling highly respected shoes when he started covering his first Wimbledon this year. He need not have worried. He has done just fine.

Consider, for example, the first two paragraphs of his story about Connors' opening match this year, after Connors had incurred Britain's wrath Connors had incurred Britain's wrath by snubbing the "Parade of Champions" at which the Duke of Kent gave out medals to past champions, commemorating the centenary:

"It was more like a Pinero evening at an old-fashioned Victorian music hall than ladies day at Wimbledon yesterday. Out strode the villain, the bad Sir Jasper Connors, to a good-natured chorus of boos and with him the hero, and elegantly archetypal young English gentleman - alias Richard Lewis from Winchmore Hill - cheered enthusiastically by his new-found army of supporters as he embarked on his task of putting the bounder in his place," Irvine wrote.

"Only this was Wimbledon, 1977, and not the era of romance. In fact, there was never the slightest chance that the audience would be treated to one of Sir Arthur's customery endings and 85 minutes later the blond Lewis lay at Sir Jasper's feet: beaten, but certainly not humiliated, by 6-3, 6-2, 6-4.

Nice lead.

"For most tennis writers, as for most tennis players, Wimbledon is the toughest professional challenge of the year," said Rex Bellamy, whose succinct, colorful and always heart felt prose graces the pages of The Times each morning.

"A Writer who wants to do a good job at Wimbledon must prepare himself, mentally and physically. His stamina must be equal to a fortnight's hard work," added Belamy, as he camly took a puff on his pipe, a swallow took a puff on his pipe, a swallow from a pint of lager ("at least I'm well lubricated"), and went to a telephone to ad-lib a 1,000-word first edition story from notes.

Wimbledon is staple front-page stuff for the evening papers, too, Little more than an hour after Virginia Wade's sensational upset of Chris Evert this afternoon, the late editions of the evening papers were being sold by shrill-voiced hawkers at the gates of All England club to the spectators heading for home.

The headline in the Evening News: "Ginny beats Champ." And in the Standard: "Wade Does it - Finally!"

In addition to the BBC coverage in the United Kingdom, Wimbledon coverage Saturday (WRC-TV-4) in Washington, noon to 6:30 p.m., sends its own crew of 72.

"As far as I'm concerned, this is the most important tennis telecast of the year. It's precedent-setting," says Dick Auerbach, producer of NBC's Wimbledon coverage.

"It is our intent to do both the women's and men's singles finals in their entirety (the women delayed one day, the men several hours due to the five hour time difference between London and the East Coast of the U.S.), and to flavor the telecast with the goings-on around Wimbledon in the centenary year," said Auerbach. "If both finals are very long, we may have to cut a bit, but we hope to get the whole match in."