TENNIS:Roger Federer and Juan Martin Del Potro serve up a Centre Court masterpiece, writes KEITH DUGGAN

ONE FOR the annals at Wimbledon, even if this story was not written by the fussy custodians of that fabled summer tournament. Yesterday, Roger Federer somehow eluded the gallant efforts of Argentina’s Juan Martin del Potro to win Switzerland’s first medal at these Games and the longest tennis match in Olympic history.

And as dusk fell, Andy Murray provoked the wildest cheer ever heard in the old ground when he beat Novak Djokovic in straight sets (7-5, 7-5). It was bedlam all around. As Murray leaped in the air at Centre Court, the lunatics had taken over the asylum and Centre Court had staged one of its most famous days.

“It was different to anything I have ever played in,” Murray said last night as the crowds chanted his name on the pavilion.

“Nothing comes close to what it was today. And you could see with Federer, he was very emotional after his match because we have guaranteed ourselves a medal now. You don’t see me smiling that much normally and I haven’t stopped since I got off the court.

“All the people who hung around outside – it was so different to what we normally experience in tennis. But the way the games went again, it needs a great final and I hope we can produce that.”

Murray’s win was surprisingly straight-forward but Federer’s semi-final with Del Potro was a duel for the ages. For four hours and 26 minutes, the players were locked in a gripping struggle that drew comparisons to John Isner’s 70-68 dance macabre with Nicolas Mahut here two summers ago.

That legendary encounter must have flashed across Federer’s mind as he surveyed the towering figure of Del Potro across the net yesterday afternoon, for the big man would not wilt.

It finished 19-17 in the third set but yet again, this haughty old shrine of English sport had left Switzerland’s favourite son with shivers down his spine. “The emotions I felt were very strong at the end. It was somewhat equal to a Grand Slam for sure. I was very touched at the end.”

From the beginning, the Argentinian offered a fascinating alternative to the bewitching skills of Federer. He stands a hulking 6ft 6in and combines the feet of a ballet dancer with the stubble and disposition of a man who has woken up after a losing a late night debate with a bottle of tequila.

Del Potro came armed with the memory of his 2009 US Open final win over Federer – he is the only player on the tennis circuit to squeeze a title out of the big three of Federer, Djokovic and Nadal in the last 30 Majors – and his huge windmill of a forehand ground stroke knocked Federer out of his stride for much of this match.

Federer stands somewhere between HRH the Queen and the ghost of Fred Perry in his popularity here at Wimbledon: he is as much as part of the furniture as the stalls selling overpriced strawberries.

The match was started after an inevitable rain delay of 15 minutes and from the beginning, it was clear Federer had the Centre Court crowd rooting for him as he chased, somewhat incredibly, his first Olympic medal.

And it was a strange day: it looked like a classic match at Wimbledon but it wasn’t. The protocol was absent. Red berets kept sentry at the gates. The Royal Enclosure was deserted.

Instead, celebrities like Kobe Bryant were scattered through the crowd. And this was an arriviste tennis set, less bothered by the prevailing etiquette of the all-lawn club and notably boisterous as the match heated up.

“Not that many ties around,” noted Federer. “I could hear babies scream from time to time. Made me feel right at home! I don’t think kids are allowed in Centre Court during Wimbledon so yeah the screaming in the stands really struck me. It was good for me.”

A swirling wind raised dust around the feet of the players as they stood at the baseline and established a pattern which soon locked them into a gripping, primal exchange. The players held serve for the first three games but even then, Del Potro signalled his intention to take the game to Federer. The Wimbledon master began to lose his sang-froid.

Trailing 15-40 on his serve in the eighth game, Federer produced three beautiful feathered backhands and yelled “C’mon” as he made it a deuce game. It was peculiar to see Federer, who at his best can float through afternoons as if under a spell, imploring himself so early. He wanted this and he was rattled by the big South American. And with good reason: a net call and a poor second service led to the break and the loss of the first set in just 36 minutes.

And for Federer, that concession hammered home the fact that he was in a roulette situation. The usual comfort of the five-set marathon was no longer an option: if he lost the second set, he was gone. Breaking Del Potro seemed like a remote possibility in the second set and so Federer was a combination of genius and anxiety. He moves like liquid gold around the court but he had to try and force the play here and so followed sublime stabbing backhands and drop-shots with some howling errors, including three forehand volleys he pushed into the net.

Del Potro was colossal in physique and heart and even if he buried his head in his towel after Federer icily won the second set tie break, he didn’t back down for a single shot. It took a heroic Beckeresque diving shot for the crowd to join the small, raucous band of Argentine fans and embrace what was an endless show of courage.

Del Potro uses that height to full advantage when he doles out those 200 kmph serves, but there is little gain in being 6ft 6in when Federer is flicking intricate little veiled returns and stun shots around your ankles. The Swiss player made the big man dance but after that heroic dive, Del Potro was clearly in pain, having crashed down on his hip.

It seemed inevitable that Federer – who still looked fresh after three and a half gruelling hours – would finally unlock the combination and break his opponent. It happened at 10-9 in that third set but as the crowd looked forward to iced teas in the sunshine, Del Potro reeled off a string of brilliant returns to leave Federer trailing by 0-40. He blew his chance to serve for the match and not for the first time, looked to the sky for answers.

“I definitely got a sense that this was something special we were both going through. The deeper we went into the match, the more I thought: ‘wow, it’s cool to be part of a match like this.’”

On it went: Del Potro’s Howitzer serves and remorseless baseline play and Federer’s uncanny all-round guile – 15-15, 16-15, 16-16 etc etc. The crowd flagged and then rallied again: they felt both trapped and didn’t want it to end. It went past the four-hour mark and officially became the longest game.

Del Potro was hobbling now but still produced wonderful defensive shots before finally breaking. The double fault Federer served at 18-17 was a measure of his nerves. He held out and finished to rapturous acclaim and then leaned on the net as the big man lumbered over.

Del Potro was fighting tears as Roger Federer drank in the acclamation, as he has done for so many summers here.

“It’s tough to speak now, I feel sad but Roger made a fantastic match,” said Del Potro before he gathered his thoughts and his tired limbs to go off and play a mixed-doubles match on the outer courts. If he was still there at 8.30pm, he would hear the delighted roars from Centre Court where Andy Murray and the Brits were in heaven. Wimbledon has its perfect final, even it’s not quite Wimbledon.