Adam Gemili ran the fastest 200 metres by a Briton for 19 years as he broke the 20-second barrier to roar into the final at the World Championships.

The 19-year-old obliterated his personal best for the second time today by clocking 19.98 seconds to win his semi-final at Moscow's Luzhniki Stadium.

It catapulted Gemili into medal contention as he went through to tomorrow night's final as the second fastest qualifier, quicker than Usain Bolt.

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Gemili is only the second Briton after John Regis to dip below 20secs.

Only American Curtis Mitchell, who ran 19.97, went quicker than him tonight.

The teenager has now taken a staggering 0.32s off his previous best in 10 hours, having gone into the championships with a PB of 20.30 and lowered it to 20.17 in the heats.

It raises the exciting prospect of what he might be capable of in the final.

Gemili, who finished 0.02 ahead of Jamaica's 100m finalist Nickel Ashmeade, told BBC2: "I can't believe it. Honestly that is the best feeling in the world. Twenty seconds, to break that, I'm over the moon.

"I didn't realise it was me. I was looking across when I crossed the line and I didn't know if I had qualified.

"I made the final and I have run a PB and I am so grateful to so many people who I have to thank, but I still have to stay focused for the final tomorrow.

"Whatever happens now, I've put myself in amongst the best 200m guys in the world. I can't ask for more than that. It's crazy, I'm speechless."

Bolt continued his smooth progression toward a seventh World Championship gold medal as he won his semi-final ahead of South Africa's Anaso Jobodwana.

The Jamaican, running in the lane outside Jobodwana, looked across to smile at him as they crossed the line, Bolt getting there first by just 0.01 in 20.12.

He said: "I was trying to take it easy, trying to pace myself. At the last minute I heard footsteps so I had to change gears a little bit."

James Ellington and Delano Williams, the 19-year-old from the Turks and Caicos Islands who has transferred his allegiance to Great Britain, both bowed out.

Ellington was fourth in Bolt's race in 20.44.

Williams, the world junior champion, who will link up with Bolt's training group in the autumn, was drawn in the outside lane and was never in contention, coming home seventh in 20.61.

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