Karsten Warholm has won a spectacular men's 400m hurdles final in a new world record time of 45.94. Rai Benjamin of the USA came second to win silver (46.17), while Brazil's Alison dos Santos wins bronze (46.72).

Both Warholm and Benjamin went under the previous world record, with the Norwegian almost a second under the former world best (46.70).

Warholm started out of the blocks like a man on fire, moving to the front from the early stages and looking for all the world as if he would saunter to victory. But the USA's Rai Benjamin had other ideas, sprinting level with the Norwegian down the final straight. It looked, momentarily, as if Warholm would fade, but as he jumped aggressively over the final hurdle, he found a new lease of life, charging over the line to destroy his own world record.

Every hero needs a nemesis, and in Benjamin, Warholm found one willing - and able - to push him to his very best. The USA athlete can content himself with a shiny silver medal - no small reward for a Herculean effort. However in any other race - in any other decade - his time would have made him a gold medallist and a world record holder.

Meanwhile, Warholm has done what no athlete in the sport has ever been able to do before, break Kevin Young's 29-year-old world record, which he did just a month ago. The Norwegian now has an Olympic gold medal and a new improved world record to add to his resume, as well as the title of Olympic champion