When Usain Bolt blazed to glory at the Beijing Olympics, he was feted as the hero his tainted sport had been crying out for. Now, having repeated them in Berlin, he can consider himself the saviour of the world championships.

When the event was changed from four-yearly to biennial it lost much of its lustre, and to many fans became just another, slightly more glamorous extension of the grand prix circuit.

While memories of Seoul, Barcelona, Sydney and Athens jump from the mind, it's far tougher to recall the exploits seen at Seville, Edmonton, Paris and Osaka.

Berlin 2009 will be different, however, and not just because of the iconic blue track and the superb 1936 Olympic Stadium that provided such a stunning backdrop.

Nobody will ever forget the place where a man first ran "9.5-something" for the 100 metres. Bolt's 9.58 still seems a barely believable time coming just a few years after 9.8 was beyond the reach of all but the absolute cream of sprinting.

The 11 hundredths of a second he took off his own world mark was twice as big a slice as any previous reduction since electronic timing was introduced around 40 years ago.

And then he did it again in the 200, clocking 19.19, also taking 11 hundredths off.

"I'm on my way to becoming a legend," said the Jamaican, who duly added a third gold, as he had in Beijing, in the sprint relay, while having to settle for the second-fastest time ever.

What makes Bolt's performances doubly enjoyable is that he achieved them with a smile on his face and without any of the posturing and trash talk that characterised sprinting in the 1980s and 90s.

On his 23rd birthday, the Jamaican spent 40 minutes walking round the stadium patiently signing autographs and joking with fans and not one person begrudged him his long-awaited Saturday night party.

Bolt, as in Beijing, was the cutting edge of another terrific Jamaican sprinting display. Shelly-Ann Fraser added the women's 100m title to her Olympic gold while they also took both relays.

Only American Allyson Felix stood in their way as she won the 200m for the third time in a row.

Less high profile but in his own way equally impressive is Ethiopian Kenenisa Bekele, who like Bolt now owns the world and Olympic titles and world records in both of his events, the 5,000 and 10,000 metres.

The 27-year-old has now won the 10,000 title four times in a row, matching the feat of compatriot Haile Gebrselassie, and is the first to achieve the double at the world championships.

Polite and unassuming, Bekele is nevertheless a fierce competitor, as shown on Sunday when he held off defending champion Bernard Lagat of the US in a home-straight duel.

The United States, as usual, topped the medal table with 10 golds and 22 in all, with Jamaica second on 7/13.

Among the most impressive American performers were Trey Hardee, with a gun-to-tape victory in the decathlon that included a marathon 12 hours in the field on the second day, and LaShawn Merritt, who followed up his Olympic 400m gold with another win over defending champion Jeremy Wariner.

The two teamed up to secure a predictable 4x400 relay gold, the US women doing the same, but there will be some hard talking after both squads failed to make the final of the 4x100 due to changeover foul-ups -- just as they did in Beijing.

And spare a thought for Tyson Gay. Running with a groin injury he clocked 9.71 in the 100 metres. The third-fastest time ever -- good enough to have won every other world championship and all but the last Olympic final yet here merely the bridesmaid's act to Bolt.

There was a world record in the women's hammer, though Anita Wlodarczyk's 77.96 metre throw was barely noticed in the cauldron of Saturday night's action. The Pole will not mind that though as she banks the 100,000 dollar cheque the record earned.

Caster Semenya was one of the few winners in Berlin who struggled to find a smile on the podium and who can blame her.

Hours before the 18-year-old was due to run in the 800 metres final the IAAF, responding to a leaked newspaper story, announced that the South African was undergoing gender verification tests following her startling improvement in times.

She deserves enormous credit for putting that, and all the speculation that accompanied it, behind her to run a perfect race and win the gold medal.