WATCH: Bizarre scenes in London as athlete forced to race alone - but still qualifies
Botswana's Isaac Makwala will go for World Championships gold after overcoming illness, quarantine and two races in little more than two hours to qualify for tonight's 200 metres final.
Makwala was on Tuesday night denied the chance to face South Africa's Wayde van Niekerk, the world and Olympic 400m champion, over one lap.
The 30-year-old, who was told he could not take up his place in the 400m final on medical grounds following illness, clocked 20.14 seconds to place second in the first semi-final heat in torrential rain at the London Stadium.
Makwala was an additional athlete in the semi-final heat, running in lane one - not normally used for the event due to the tightness of the bend - after qualifying via a time-trial earlier yesterday evening. He qualified for tonight's final behind the United States' Isiah Young, who won the semi-final in 20.19secs.
Makwala celebrated by raising his right arm aloft. The Botswana athlete had been given medical dispensation to withdraw from the 200m heats on Monday night. Without a valid reason for pulling out, he could have been disqualified from the 400m final - an event he was forced to miss under protocols imposed by Public Health England.
His 48-hour quarantine expired at 2.0pm yesterday and the IAAF accepted a request from Botswana to allow Makwala to try to qualify for the shorter event.
And he succeeded before immediately departing to prepare for the semi-finals.
Van Niekerk received his 400m gold medal before he qualified as the second of the fastest losers in the 200m after finishing third in his heat in 20.28.
The IAAF had earlier been forced into a further rebuttal to claims from Makwala that "sabotage" led to his exclusion from the 400m final.
Makwala told ITV on Tuesday night "maybe this is sabotage" and told the BBC on yesterday "there's something fishy they don't want to tell us".
However, the IAAF dismissed his allegations as "absurd". An IAAF spokesperson said in a statement: "There is nothing we want more than extraordinary competition at these championships. We freed up the competition schedule here to allow this to happen between these two athletes over 200m and 400m. To suggest otherwise is absurd."
Olympic medallist Kelly Sotherton urged a note of caution on Twitter, saying: "Allowing #makwala to run a 200m race alone in a bid to qualify now has set a precedent for others. Regardless of what the situation is."
Meanwhile, Phyllis Francis of the United States won a dramatic 400 metres gold last night. Her compatriot Allyson Felix was chasing a 10th world title in defence of the 400m gold she won in Beijing two years ago.
But Felix's third-placed finish on a cold night in torrential rain at the London Stadium was not the main talking point.
It had appeared Bahamas' Shaunae Miller-Uibo would add the world title to the Olympic gold she claimed with a dramatic dip in Rio. But her late implosion on this occasion was almost as dramatic. Miller-Uibo was leading down the finishing straight, but stumbled in the final 20 metres to miss out on the podium, finishing fourth in 50.49 as Francis won in 49.92.
Salwa Eid Naser of Bahrain took silver in 50.06 and Felix bronze in 50.08.
Former decathlete Karsten Warholm of Norway won the men's 400m hurdles final in 48.35. Olympic champion Kerron Clement of the USA had to settle for bronze in 48.52 as Turkey's Yasmani Copello took silver.
Meanwhile, Mo Farah remained on track for a golden double at the World Championships, but refuses to take a fairytale finale for granted.
The 34-year-old finished second in his 5,000m heat in 13 minutes 30.18 seconds and is now eyeing Saturday's final ahead of his planned track retirement at the end of the month.
Farah has already won the 10,000m - Great Britain's only medal of the championships so far - to defend the title he won in 2013 and 2015. And a double defence is on the cards after Farah shrugged off a knee injury and a cut leg, having been spiked in his 10,000m triumph.
Farah is wary of missing out on gold after Usain Bolt, retiring after the championships, only won bronze in the 100m on Saturday.
He said: "You've seen it with Usain Bolt, it happens. It would have been nice to see him win but it didn't happen and no-one is going to give it to you - no matter who you are, even Usain Bolt.
"I just have to now focus on myself and get ready. It would be pretty amazing - no-one has every done it. It would mean the world to me but at the same time I don't take it for granted."
World Championships, Live, BBC 2, 6.0pm