Decorum reigns supreme at Wimbledon, a bastion of middle class gentility where the stiff upper lip never trembles on the hallowed centre court.

At the Australian and US Grand Slam tournaments, crowds whoop and holler for their favourites and French crowds sometimes love to boo any sign of gamesmanship from a player.

Not so at Wimbledon where etiquette is everything.

The programme for the world's most famous tennis tournament even warns fans how to behave:

-- Do not make a noise during a rally.

-- Do not applaud a net cord or double fault.

-- Gentlemen are requested to keep their shirts on.

-- No babes in arms are allowed in any show court.

All that is half the attraction for the legions of middle-aged, middle-class couples who troop up from the country on their annual pilgrimage to Wimbledon.

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After sipping champagne and quaffing strawberries and cream at elegant picnics, the fans stroll into the centre court stands in orderly fashion.

"It certainly does reflect the British character," said Wimbledon spokesman Johnny Perkins.

"This is all part of a quintessentially British experience -- echoes of tennis and croquet in an English country garden with everyone enjoying themselves."

The contrast could not be more stark with the raucous football stadiums and the "barmy army" of fans who follow cricket. Golf is the nearest equivalent, Perkins argued.

"The two are fairly comparable. Both sets of fans have the knowledge and the respect for the players and their fellow fans," he said.

"The Wimbledon crowds are both knowledgeable and sporting. A lot of the people who come here are tennis players," he added.

Wimbledon crowds also revel in that perennial conversation topic -- the weather.

In the inevitable rain breaks that constantly pepper Wimbledon, they sit huddled under umbrellas stoically sipping tea from a thermos and glancing hopefully at the sky.

Bookmakers are even offering odds of 33-1 for rain to interrupt or delay play on centre court every day over the next two weeks while incurable optimists were offered odds of 8-1 that it will stay dry throughout the tournament.

The streaker is a perennially popular bet with bookmaker William Hill offering odds of 5-1 that a naked fan will leap on court during the men's final and 4-1 for the ladies final.

Decorum may be the order of the day among the fans but definitely not among the players, bookmakers believe.

"It's a 100-1 shot that there will be no argument between a player and an umpire during the tournament. The spirit of John McEnroe is alive, well and still arguing," spokesman Graham Sharpe said.

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