Some time Monday morning, after the dew dries and before the gates are thrown open, 12 gallant reapers will shave a millimeter of grass off the lawn of the All England Lawn Tennis Club and Wimbledon will begin. "They're my courts," said Jim Thorn, the head grassman. "I'll let the players play on them. I don't like to see them not being used."

For the next two weeks, Thorn will graciously step aside and open his lawns to Jimmy Connors and Martina Navratilova, the defending champions and favorites; to John McEnroe and Chris Evert Lloyd, former champions and last year's runners-up.

Both men and women will be competing on opening day. And in an even more radical departure, matches will begin at 12:30 p.m. on the court outside the stadium, though Connors as defending champion will play the first match on center court beginning at 2 p.m.

The consensus is that this 106th Wimbledon tournament belongs to Connors, McEnroe, Navratilova and Evert Lloyd, though it can't possibly be as cut and dried as it and Thorn's courts appear.

He even wishes Ivan Lendl well, though Lendl stayed away last year, claiming an allergy to Thorn's lawn. "This should suit Lendl's game," he said. "I'm hoping it will. I'd like to see him do well here. They're my courts. He's run grass down. I'm a grassman. Hard courts are not in my vocabulary. He's got to be big enough to play on grass courts."

This spring has been Britain's wettest in memory. It rained and poured for 37 days, three short of the biblical record. Two weeks ago, the sun came out and, save for a sprinkle earlier this week, it has been dry.

Rarely have the courts looked better. "It's like the '60s," said Billie Jean King, seeded 10th and one of the few players competing who can remember that far. "It's like concrete. They're a lot faster but they're a lot truer, too. Everyone has been trying to figure out who it helps. If you hit a good flat shot, it goes. A chip is good. But it also bounces higher. If you volley, the volley takes. The last few years, it went phfffft, and the guy could go whack."

Bad courts are an equalizer. Good courts should bring out the best in the best. "They should make the quality better," King said.

Because the courts are fast, they should help serve-and-volleyers like McEnroe and Navratilova. But McEnroe injured his shoulder during his loss to Connors last week. Navratilova has lost only one match this year but comes into the tournament without a victory in the last three Grand Slam events and without her coach, Renee Richards. Dismissed after Navratilova lost to Kathy Horvath in the French Open, Richards has been replaced by Mike Estep.

If the bounces are true and high, they should help Connors and Evert. "If the bounces are better, it's going to help guys with good ground strokes," said Ray Moore, a former player. "They'll have a good hit at the ball."

Connors has been playing so well that people abandon the English language in an effort to describe his play. "Rrrrr," said King. "He's just pouncing."

"I know Connors likes grass," said Thorn, who doesn't play any. "This particular grass he'll love."

Thorn came to Wimbledon in March 1982 from St. George's Hills Lawn Tennis Club 17 miles away. He has been a grassman for 35 years since health problems forced him to abandon maintenance engineering. Though he was in charge during last year's deluge, he was not really responsible. The important preparations are done in the fall. Only cosmetic work goes on in the spring.

Last fall, Thorn went to work in earnest to retrieve Wimbledon's lawns. "Different grass, different methods, different everything," he said. "We introduced a new grass seed mix to combat wear and recover quickly. We're using a different soil for top dressing. And our repair methods--I'm looking for the right word--are more violent.

"We mechanically rake them until you think you've absolutely ruined them and that is nearly enough. You do it once more after that. Then we've got a hollow coring machine, an American machine, with three-inch cores and two-inch centers. It takes a three-inch core out every two inches and virtually removes 19 percent of the entire surface. We discard that and put new soil in and oversow the whole area whether it needs it or not."

Thorn, 57, paused, using two hands to roll a cigarette, as he stared at one of his beauties. His visitors were impressed with his dexterity. "I'm not a cowboy," he said.

The courts also require many hands, some rolling, and some cooperation from the deities. He has asked them for a nice one-hour drizzle. That's all. "The sun has helped, the rain has helped," Thorn said. "But don't just let people say the weather has done it. My 12 men have done it."

Two of them are his sons Michael, who took his job at St. George's, and Phillip.

Clearly, these are not just any lawns. Crabgrass? Perish the thought. "We do not have crabgrass," he said. "We don't talk about crabgrass. It's a dirty word at Wimbledon. It doesn't exist. It wouldn't dare."

Someone asks if the courts are ever sprayed with green paint the way some football fields are in America for television. Unthinkable. "Lush green is lovely for television," he said. "It is terrible for tennis."

If the courts were too green, he said, "I'd be worried sick. I want a yellowy green."

Which they are. "They'll get better next year," he said. "They'll be perfect the year after that."

When he was at St. George's, Thorn was sure his courts were the best in the world because they were his. But Wimbledon is a grassman's paradise. After this, he says, "you retire or get sacked."

He lives in a cottage on the grounds of the club. He has a lawn and a garden but he doesn't putter. "I hate gardening," he said. "The wife grows the tomatoes."