Athletics: Caster Semenya's return to Berlin eclipsed by 800m world record breaker

Rudisha's run came at the Olympic stadium in Berlin, where he was a semi-finalist in last year's World Championships.

Semenya famously won the women's event in the same championships in a stunning time of 1:55.45, finishing well clear of the field.

However, the South African was then at the centre of a storm of controversy as doubts were raised about her gender, the 19-year-old eventually being cleared to run again on 6 July this year.

She won her first two races back in low-key meetings in Finland, clocking 2:04.22 and 2:02.41, but improved significantly yesterday to dip under two minutes with a time of 1:59.90.

Speaking about his semi-final exit in Berlin last year, Rudisha told the IAAF website: "Last year I had a bad time in Berlin. The weather was not very good and I did not make the final so I did not want to talk too much about the world record before today's race.

"But I knew it was my day. I trained very hard, the weather was good. I told the pacemaker to run the first lap under 49 seconds and he did a great job.

"The last 200m I had to push very hard but I saw the clock (showing] 1:41.09 at the end. Fantastic, I am very happy to be the fastest 800 metres runner in the world."

Semenya cannot yet claim that accolade but was pleased to be back under the two-minute barrier. "It feels good to be back in Berlin," Semenya said. "I did not think about everything that happened after my gold medal, I just concentrated on my race and time.

"My goal was to run under two minutes and I did. After my training I was a little disappointed with my competition results this year, but now I am happy because I can see the progress.

"My next competition will be in Brussels (next Friday] and then I am looking forward to the Commonwealth Games (in Delhi in October]."

Meanwhile, Asafa Powell appears set to be the latest star athlete to pull out of the Commonwealth Games. The reigning Commonwealth 100 metres champion Powell has been suffering from back and hamstring problems that forced him to withdraw from yesterday's meet in Berlin, and that may prompt him to skip an event already dogged by withdrawals.

"A final decision is imminent, but it's looking extremely unlikely at best that Asafa will be in India," said his agent Paul Doyle.

Fellow sprint star Usain Bolt has already pulled out, alongside several who would have carried medal hopes for Britain including Paula Radcliffe, Jessica Ennis, Jenny Meadows, Natasha Danvers, Sir Chris Hoy, Bradley Wiggins, Victoria Pendleton and Beth Tweddle.

The issue of security at the Games was raised again last week by Australian swimming legend Dawn Fraser, who called on her country to boycott the event because she fears athletes will be put in danger by attending.