Essex middle distance star Andrew Osagie ran a personal best to claim third place in the 800 metres at the Diamond League meeting in Doha.The 24-year-old Olympic hopeful crossed the line in one minute 44.64 seconds, with world record holder David Rudisha of Kenya winning the race in a world-leading time of 1:43.10secs. Britain's Michael Rimmer finished sixth in 1.44.86. Perri Shakes-Drayton was also third in the women's 400m hurdles in 55.25, as Jamaica's Melaine Walker won the race in 54.62, the best time of 2012 so far. American sprinter Justin Gatlin beat Jamaican rival Asafa Powell by a hundredth of a second in the men's 100m. Powell led from the gun before Gatlin powered back in the final 30m to win the race in a fast time of 9.87. American sprinter LaShawn Merritt was victorious in the 400m as Martyn Rooney, sixth over the distance at the 2008 Olympics, came fourth. Merritt returned to the track last year after being banned for almost two years for a doping offence.