You cannot be serious! Oh yes we can, Mr McEnroe: the umpires and linesmen of the world of tennis have much better eyesight than the players, a fact for which they rarely get credit.

Famous for his disputes with officials over whether a ball was in or out of the court, the one-time enfant terrible of Wimbledon was more likely to be wrong than right, a scientific study has found. John McEnroe wouldn’t agree, of course.

Using evidence from the Association of Tennis Professionals, George Mather, of the University of Sussex, has concluded that while players and line judges can be prone to error when assessing where a ball has bounced, because of what he calls “inherent limitations of human perceptual vision”, the officials are significantly more accurate.

Dr Mather conducted his research after the introduction in 2006 of the Hawk-Eye electronic line-calling system, which has revolutionised the sport. Today, many of the sport’s biggest courts are equipped with instant replay screens that supply quick-fire judgment on where the ball has landed — to within three millimetres.

The system is not universally popular. Roger Federer, for example, the world No 1 and 12-times grand slam tournament champion, openly despises it.

Whatever its faults or merits, Hawk-Eye was not available in the days when McEnroe railed against the umpires. He was young, ambitious, lippy and feisty; they were elderly, autocratic and probably blessed with less-than-perfect eyesight.

Whatever the reasons, they used to annoy the tennis shorts off him. But they, in turn, may have been wrong as often as McEnroe accused them of being. Dr Mather used information from 1,473 Hawk-Eye challenges made by 246 players or doubles pairings during 15 tournaments in 2006 and 2007. Of those, 39.3 per cent were successful, indicating that line judges can make mistakes too. “The judges perform more reliably than the players, but they do make a significant number of mistakes,” Dr Mather concludes. “That suggests players should certainly use their full quota of challenges, because some errors are inevitable and they have little to lose.”

More errors occur on the base and service lines, which run horizontally across the court, than on the side or centre lines. The reason, Dr Mather says, is that the judges on the base and service lines sit side-on to the court, and the ball flashes past them in a blur. “For the players, it is certainly worth thinking harder about challenging calls made on the cross-court lines. However, they should bear in mind that they are also more likely to get these wrong themselves.”

The research found that 94 per cent of challenges featured balls that bounced within 100mm of a line — less than twice the diameter of the ball itself. That, Dr Mather claims, suggests strongly that players challenge when they genuinely believe that a mistake has been made, rather than using it as a ploy to unsettle an opponent or to buy vital seconds to rest before a critical point. “It seems to be a case of players believing they are right on balls that are literally too close to call, and not gamesmanship.”

Tennis officials welcomed Dr Mather’s findings. Gerry Anderson, a University of Sussex graduate who has umpired seven singles finals at Wimbledon, said: “Everybody knows that we officials make mistakes, but Hawk-Eye has proved we make far fewer than players in general think we do.”

From next year the number of challenges a player is allowed will rise from two to three, with one additional one in the event of a tie-break.

Federer, however, remains unimpressed by Hawk-Eye. “Now the umpires can hide even more behind these calls. It makes it really hard for us. They tend to now just let us do the work, the tough stuff. They let us get embarrassed, basically,” he said recently.

And if Hawk-Eye had been around in McEnroe’s day, Wimbledon wouldn’t have been half as much fun.

Moments of madness

“You cannot be serious man! That ball was on the line! Chalk flew up!”
To an umpire at Wimbledon, 1981

“I’m not having points taken off me by an incompetent old fool. You are the pits of the world.”
At the same tournament

“You must arrest him. He is the worst umpire I have ever seen.”
Begging a policeman for help, also at Wimbledon

“Answer my question! The question, jerk!”
To an umpire at the Stockholm Open in 1984

“You are the worst umpire I've seen in my life. You’ll never work another one of my matches.”
To an umpire at the Paris Open, 1986

“Do you have any problems, other than that you’re unemployed and a moron and a dork?”
To a heckling fan at Key Biscayne, Florida, 1992

“If you believe that, I’ve never questioned a call in my life.”
On Anna Kournikova’s claim to be a virgin, 2000.

“Now I get docked 10 to 20 per cent [of my appearance fee] if I don’t yell at people and break a racquet.”
On expectations of him on the seniors’ circuit, 2000

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