Rooney is making his Olympic debut in Beijing
Great Britain 400m runner Martyn Rooney tuned up for the Beijing Olympics by smashing his personal best for the second time in three days.
The 21-year-old powered down the home straight to claim victory ahead of Ricardo Chambers and Leslie Djhone at the Monaco Grand Prix in 44.72 seconds.
Rooney's success came after he broke the 45-second barrier for the first time at last week's London Grand Prix.
The men's 400m heats in Beijing begin on 18 August.
Rooney's victory in Monaco lifted him back to the top of the European standings and to ninth in the world rankings.
The Croydon runner said after his landmark performance at Crystal Palace last weekend: "If I don't make the final at the Olympics now it'll be a bad championships.
"Then if I get a good lane in the final, who knows?"
American defending champion Jeremy Wariner is favourite to retain his Olympic title in China as he leads the world rankings with a time of 43.86 secs.
Compatriot Lashawn Merritt is also expected to get amongst the medals.
Rooney and Andrew Steele represent Team GB in the individual 400m while Rooney's PB will boost hopes of a strong performance in the 4x400m relay.