Josh Kerr won a surprise Olympic bronze in the 1500m, Britain's first in the distance since 1988, as Norway's Jakob Ingebrigtsen won gold in a Games record time.
Kerr ran a superb final lap and almost overtook world champion Timothy Cheruiyot on the line, but it was the Kenyan who claimed silver.
It is the 23-year-old Scot's first major medal and Ingebrigtsen's maiden global title.
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In hot conditions on the final day of track and field, Britain lined up with three in the 1500m final for the first time since Seoul 1984, when Sebastian Coe won gold ahead of Steve Cram, and Steve Ovett was unable to finish.
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Wightman looked impressive in the rounds leading up to the final, but he finished 10th behind team-mate Jake Heyward. Kerr dealt with the conditions brilliantly and looked strong in the final 400m, battling with Abel Kipsang.
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The pair were neck and neck and exchanging third and fourth, but Kerr found a new burst of pace on the final straight to streak clear of Kipsang. Now he had Cheruiyot in his sights.
The Kenyan was tiring quickly and Ingebrigtsen was clear, but he held off Kerr, who ran the race of his life in a personal best of 3:29.05, a mark which itself would have been a new Games record.
Ingebrigtsen won what will surely be the first of many medals, as the 20-year-old fulfilled his potential to triumph in 3:28.32, which was also a European record.
"It's the craziest feeling, you're pinching yourself," Kerr told Eurosport.
I've looked at this Olympic championships for the longest time. I said before I was going to throw my whole life at it, I'm goin to run a PB, I'm going to run under 3-30 in the Olympic final and everyone was like, what are you talking about? There's money to be made in other races.
"This was it for me. I can hang my spikes up now for this year and get ready for next year. I'm switched off.
"I don't really care about smaller races, it's about building up to these major championships and making that time count".
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