South Africa's Van Niekerk wins 400m in 43.48 seconds
Gatlin (19.87) & Bolt (19.96) win their 200m semis
GB's Zharnel Hughes wins his semi in 20.14
Eilidh Child sixth in 400m hurdles final
Dina Asher-Smith fastest qualifier in 200m heats
13:46 BST
The final 200m semi-final of the day and the cameras are focusing their lenses on Usain Bolt. Britain's Danny Talbot is running on the Jamaican's outside.
Kei Takase (Jpn)
Miguel Francis (Ant)
Ramil Guliyev (Tur)
Kenji Fujimitsu (Jpn)
Anaso Jobodwana (SA)
Usain Bolt (Jam)
Daniel Talbot (GB)
Roberto Skyers (Cub)
Colin Jackson
Two-time world 110m hurdles champion on BBC TV
Quote MessageGatlin thumped everyone on the bend, he is the man in form, the world leader at this distance and you can see why.
Darren Campbell
Former British sprinter on BBC Radio 5 live
Quote MessageGatlin exploded out of the blocks and was able to coast in the straight. He crumbled under the pressure in the 100m but to run this time in the semi-finals shows there's no fitness issues, it's whether Bolt can put the pressure on him again.
Image source, Getty ImagesJustin Gatlin ahead after 100m and while Alonso Edward (20.02) and Femi Ogunode (20.05) close in on him with the finishing line nearing, the American comfortably wins in 19.87.
Michael Johnson
400m world record holder on BBC TV
Quote MessageIt was not the best of starts from Zharnel Hughes but he looked very comfortable on the curve and handled himself very well. He runs like an athlete who is far more experienced and I was very impressed. He has put himself in a good position to get a medal.
13:38 BST
Justin Gatlin is in the second semi. "He who must not be named," says Andrew Cotter in the commentary box.
Sixteen-year-old Abdul Hakim Sani - who won his heat - in this race, too.
Reynier Mena (Cub)
Jeremy Dodson (Sam)
Alonso Edward (Pan)
Julian Forte (Jam)
Femi Ogunode (Qat)
Justin Gatlin (USA)
Yancarlos Martinez (Dom)
Abdul Hakim Sani Brown (Jpn)
Quote MessageI hit my toe on the bloke and that slowed me down when I got out, but nevertheless I am in the final that is what I wanted and I have a good lane draw. I am ready to run against the best guys in the world.
Zharnel Hughes after winning his 200m semi-final
How good was Zharnel Hughes' performance? He pushed Jamaica's Nickel Ashmeade (20.19) into second and Dutchman Churandy Martin (20.20) into third.
Familiar names failed to qualify - with Christophe Lemaitre fifth and Warren Weir seventh.
Darren Campbell
Former British sprinter on BBC Radio 5 live
Quote MessageZharnel Hughes could go on to break the British record and could get a bronze medal. That was a fantastic, professional run. He didn't ease down too early. He wanted one of the middle lanes and to be taken seriously as a contender.
How good is British champion Zharnel Hughes? The Briton crosses himself before he places both hands on the track in preparedness for lift-off.
Everyone comes out of the bend shoulder-to-shoulder, but Zharnel Hughes nips ahead, clocking 20.14. He's through to the final.
13:30 BST
Before we talk more about Justin Gatlin and Usain Bolt, we must focus on the first heat which features Britain's Zharnel Hughes. Here's how they line up:
Nickel Ashmeade (Jam)
Akani Simbine (SA)
Warren Weir (Jam)
Churandy Martina (Ned)
Likourgos-Stefanos Tsakonas (Gre)
Zharnel Hughes (GB)
Brendon Rodney (Can)
Christophe Lemaitre (Fra)
"I’m feeling tired,” said Usain Bolt on Tuesday after clocking 20.28 seconds to reach the 200m semi-finals. But a champion doesn't rest.
The Jamaican, who his hoping to win a third consecutive 200m world title, must go again. And hopefully again, if he reaches the final.
Bolt's drawn in the third semi-final and will set off at around 13:46 BST.
Image source, BBC SportJustin Gatlin and Usain Bolt are never away from the Bird's Nest. The world's two premier sprinters are racing around half of the track again at bullet speeds in a bid to reach the 200m final.
Gatlin, the world 200m champion in 2005, has been dominant in this event this year, running three of the five fastest times of the year, but we've learned from Sunday's 100m final that setting world leading times counts for nothing at a major championship.
Image source, BBC SportQuote MessageSixth in the world is a great achievement but I felt I let myself down a bit. I felt I could have got a medal. I am going to take this motivation and hopefully do something at the Olympics next year.
Eilidh Child after coming sixth in the 400m hurdles final
Colin Jackson
Two-time world 110m hurdles champion on BBC TV
Quote Message"Hejnova is brilliant and has a lot of patience, she has a good technique and good rhythm. Even when there are distractions around her she keeps a cool head which is crucial when it comes to the final two barriers and that is why you see her run a new world lead and take the title.
Michael Johnson
400m world record holder on BBC TV
Quote MessageIt was always going to be a tough race for Eilidh today She was not in a lane close to Hejnova and Little and was not able to get into the mix.
Yego's history-making meant our attention was sharply drawn away from the women's 400m hurdles final. For those of you wanting a bit more information, Eilidh Child came sixth in 54.78.
"I feel like I've let myself down a bit," says the Briton.
Silver? Shamier Little in 53.94. Perhaps more athletes will now start wearing bows in their hair. Bronze went to Cassandra Tate (54.02) to complete and American two-three.
Allison Curbishley
BBC athletics expert on Radio 5 live
Quote MessageJulius Yego is on billboards everywhere in Kenya. If he was a legend already in Kenya he's now elevated himself to icon. He will enjoy every moment of this. Another medal for Kenya - they are taking over the world!