Usain Bolt secures 11th World Championships gold with relay win
Usain Bolt collected his 11th World Championships gold medal as Jamaica won the 4x100m relay in Beijing, while Great Britain failed to finish.
Bolt anchored his quartet to a world leading time of 37.36 seconds.
GB were third going into the final changeover but James Ellington did not get the baton to anchor Chijindu Ujah.
The USA finished second but were disqualified after a faulty final changeover, meaning China were promoted to silver and Canada bronze.
It was Bolt's third gold of the championships after victories in the 100m and 200m.
The Jamaicans completed a sweep of the sprint relays with the women, anchored by 100m champion Shelly-Ann Fraser-Pryce, also winning.
Great Britain's women's relay team of Asha Philip, Dina Asher-Smith, Jodie Williams and Desiree Henry set a new national record of 42.10secs as they finished fifth.
GB men from good to bad
The British team had qualified in a season's best time, but Harry Aikines-Aryeetey was replaced by sub-10 second runner Ujah for the final.
Aikines-Aryeetey, who was also celebrating his 27th birthday, tweeted his disappointment at the decision and then retweeted messages from followers questioning why he wasn't in the team.
Britain had looked in contention for a medal after a strong start by Richard Kilty and then Danny Talbot on the second leg.
But it was the changeover between Ellington and Ujah that ruined their chances, with Ellington not close to reaching his team-mate with the baton and questioning whether Ujah had gone off too soon.
"We were easily in the running for a bronze," said Kilty, who could be seen in a heated discussion with Ellington after the race.
"It's not a team we've practised a lot. We messed up on the third change."
Ellington added: "My speed was OK, I need to watch it back. Maybe CJ [Ujah] went a bit early."
Bolt came up with a simple solution for Britain's relay problems, the latest in a long line of mishaps in finals.
"They're taking it too serious," he said. "They have camp after camp after camp after camp to try to perfect something but it just comes natural - sometimes you just need to go out there and run."
American Ashton Eaton broke his own decathlon world record as he successfully defended his world title.
The 27-year-old, who led overnight, needed to run 4:18.25 or faster in the final event the 1500m to score the 824 points needed to break the record.
And he ran 4:17.52 to finish with a record 9,045 points haul.
"In the 1500m, I was having doubts, I didn't know if I could do it," said Eaton who is the only athlete to break a world record at the Championships.
"I could see the Algerian Larbi (Bouraada) in front of me and I used him. I could tell, he sped up. I caught up again and he sped up again. So I thank him for that."
Best of the rest
Britain's Shelayna Oskan-Clarke finished fifth in the women's 800m as Marina Arzamasova of Belarus won gold.
Great Britain's men's and women's 4x400m relay teams both qualified for Sunday's finals.
The men's team of Rabah Yousif, Delano Williams, Jarryd Dunn and Martyn Rooney won their heat in a season's best time of 2:59.05.
The women's team finished second in their heat, the quartet of Eilidh Child, Anyika Onuora, Kirsten McAslan and Seren Bundy-Davies also setting a season's best time of 3:23.90 to secure automatic qualification.
Mariya Kuchina, 22, won the women's high jump with a lifetime best clearance of 2.01m. Croatia's Blanka Vlasic, 31, and 33-year-old Russian Anna Chicherova also cleared 2.01m but had had failures earlier in the final and had to settle for silver and bronze respectively.
Poland's Piotr Malachowski, the silver medallist in 2009 and 2013, claimed his first discus world title with a throw of 67.40m.