Sideline Cut: Maria Sharapova may be the new darling of Wimbledon but Martina Navratilova remains its irreplaceable icon. Her appearance at this year's Wimbledon is, for many viewers, like a portal back to the golden age of professional tennis. On Thursday night, as the headline writers at Canary Wharf conjured up bold headlines to match the front page photographs of the willowy, solemn teenager, the 47-year-old Navratilova was treating a few hundred tennis lovers to a classic treat on court 13.

Playing in the mixed doubles third round with Leander Paes, the greatest female player ever got sucked into a deadlocked battle of nerves and soul with the Black family, Cara and Tim, from Zimbabwe.

What sets Wimbledon apart from other famous sports tournaments is that it manages to absorb the hard-nosed reality of sport into its hopelessly outdated and foolish attempts to recreate the England of Brideshead Revisited. The strawberries-and-cream motif is just the tip of the nostalgia: if the good folk of Wimbledon had their way, it would be straw hats, ginger beer and low jazz on the gramophone all the way.

Given that even God has given up waiting on Tim Henman to end the Arthurian search for an English champion of the All-Lawn tennis club, you have to admit there is something touching and elegiac in the way the locals cheer him on anyway, invoking the old Dunkirk spirit.

Wimbledon is the befuddled, bespectacled grand-aunt of professional sports events, posh and a bit absent-minded and unintentionally funny. It cradles the last of old England: even the umpires look and sound as if they are just taking holidays from the day job playing Henry V at the Old Vic.

Because Navratilova was the dominant figure of her game through the late 1970s and early 1980s, when tennis - and in particular Wimbledon - captured something of the spirit of the day, her longevity is to be cherished. In 1975, when she decided to defect from Czechoslovakia while playing the US Open, Navratilova put herself in a loveless situation, first denounced and then all but erased from existence in her native country and regarded as an oddity in the free West. The emerging rivalry between the stern and bespectacled Navratilova and the peachy All-American Chrissy Evert seemed loaded with political implication, just as Bobby Fischer's chess rivalry with Boris Spassky became something darker and weightier.

Like many tennis stories, Navratilova's early years were all about hardship, and the price she paid in forsaking the grimness of communist Czechoslovakia was the possibility of never seeing her family again. She never seemed to shirk the hard responsibility, and her decision to declare herself gay probably instantly cooled the public warmth she worked hard to build up.

They say you get the face you deserve, and in her fifth decade the overwhelming expression on Navratilova's is of integrity. Her features seem to have softened over the years, and as the great icons like Evert, Borg, McEnroe and Connors gradually faded from the scene, her continuing presence has become a comfort, as if she were waging a battle of wills with Father Time. Superbrat went grey, old Dan Maskell shuffled off and prodigies appeared and vanished overnight. Through all this, Navratilova kept playing and, after a brief retirement - she claimed it was while commentating at Wimbledon that the old bug returned - she resumed what is a completely joyful and admirable relationship with her sport.

Besides remaining a quite phenomenal athlete, she has managed to stay competitive despite amassing a ridiculous total of 58 grand slam titles. In the game against the Blacks on Thursday night, she missed by millimetres a volley to win the match and thus drew herself and her partner into a deathless struggle with the young South African kids. The real charm of Wimbledon is not the pomp and ceremony of the Centre Court but the doubles games that are played on the edges, late into the evening.

Navratilova was still playing at nine o'clock on Thursday night, with light fading over south London and dew settling on the court. They were like kids rushing to finish a game of soccer before getting called in for tea. There was the sense that the other Wimbledon courts were long deserted: that the players would have to turn out the lights and pull the latch when they were done. Play was halted at around 9.15 p.m., by which time Sharapova was causing the ripples on the evening news bulletins.

There are parallels to be drawn between the latest starlet and Navratilova, who won her first Wimbledon a decade before the Russian girl was born. Each had a tough childhood in which tennis played a central role. Both worked extraordinarily hard and probably experienced few laughs in their early years. The difference was that Navratilova lived with her mother near Prague until she was 18. Sharapova headed off to the tennis hothouses of Florida to go through a regime of training that surely is as undesirable as the state sports programmes that were organised in countries like Navratilova's former motherland.

Sharapova is obviously mentally resilient and committed to her game, and looks to be indifferent to the clamour for her to fill the role as eye-candy in a sport that has remained glued to a chauvinistic and sexist sensibility when it comes to its female athletes. Tennis commentators are already urging her to take stock of the short and pointless career of the game's original blonde-with-killer-smile, Anna Kournikova.

Instead, Sharapova would be better advised to take some time to study the greatest of them all. Before she has even played her first major final, she was asked about her interests outside the game and she said that tennis was not her whole life.

And that is often the abiding sense with modern tennis players - and all professional athletes: that it is a career, a job at which they happen to excel.

Navratilova made an exceptionally wealthy lifestyle for herself while all the time conveying the impression that, for her, tennis was never anything less than a precious expression of self: it was her craft, and even though she came closer than anyone else to perfecting it, she is still honing it. So if Sharapova, the fashion of this year's tournament, is crowned as the first lady of Wimbledon this afternoon, she could do worse than consider the philosophy of a player who has been in her place nine times before.

Given the reckless abandonment of tennis lives today, it is highly unlikely Navratilova's record will be matched. Nor will her longevity. In a way, Navratilova has achieved the impossible: she has managed to stay in the game she loves probably longer than is wise without sacrificing any of her dignity. She has managed to keep playing for the sake of playing and she is still a contender. You can't hope to do any better than that.