Gold medals never come easy, but Mo Farah’s third was harder than most. First Farah fell, and then he found himself in a fierce final sprint with Kenya’s Paul Tanui. Farah won in 27min 05.17sec, and by a little less than half a second. Afterwards, of course, we saw that familiar grin, and were treated to the Mobot all over again. But in the press conference that followed the medal ceremony Farah faced a hard question about his association with the Somalian coach Jama Aden, who was arrested by the Spanish police on doping charges last June. At the time British Athletics explained that Aden had worked as an “unofficial facilitator” for Farah in 2015, and that all he had done was “hold a stopwatch”. Four years on from the London Olympics, the atmosphere is different now.

Facebook Twitter Pinterest Mo Farah celebrates on the podium with second placed Paul Kipngetich Tanui (left) of Kenya and third-placed Tamirat Tola of Ethiopia. Photograph: Yoan Valat/EPA

A journalist wanted to know why Farah, as a clean athlete, kept such associations. He asked about a photo of him and Aden together. “Obviously it is a small sport,” Farah said. “There are so many athletes who compete, so getting pictures with someone who asks you to take a picture, you’re not going to say no, are you? It doesn’t mean I’ve trained with him.”

Farah continued “Obviously I believe in clean sport and we’ve got to do what we can, but at the same time you can only control yourself.”

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It left a sour note, but Farah shouldn’t be immune to interrogation any more than any other athlete. The truth is that a lot of winners here will face their own versions of these questions in the next week. That’s the the sorry state the sport is in.

Back to Farah’s achievement, then, on a night when there was no repeat of London’s Super Saturday as Jessica Ennis-Hill and Greg Rutherford couldn’t quite match their 2012 golds, settling for heptathlon silver and long jump bronze respectively. Farah is the sixth man to win two Olympic 10,000m titles, following on from Paavo Nurmi, Emil Zátopek, Lasse Virén, Haile Gebrselassie and Kenenisa Bekele. If he wasn’t there already, Farah now ranks high in his sport’s hall of fame. If he wins the 5,000m next week, he will be only the second man, after Virén, to win both Olympic titles twice. Virén famously fell too, when he won the 10,000m for the first time in 1972. He got tangled up with Emiel Puttemans, but got back to his feet and hared back into the race. Which is exactly what Farah did, 44 years later.

For ten laps, Farah barely seemed to stretch his legs. He waved to his family in the stands as he came around the second bend, then coasted at the very back of the pack right through the first 1,000m, thinking it the safest place to be. Soon after he decided to make a move, and slid past the field so he could lurk behind the frontrunners. The American runner Galen Rupp was just behind him. And that’s when it happened. “There was a lot of pushing,” said Rupp, “guys slowing down in front of him.” They collided, and Farah tumbled down to the ground as another runner hurdled over him. For an awful moment, it looked like his race was over.

Farah rolled, regained his feet, and regathered his pace. “When I fell I was just thinking ‘try and get back as fast as I can’,” Farah said. “I was thinking ‘don’t panic, don’t panic, don’t panic’.” Rupp helped. “I wanted to make sure that he was OK first and foremost,” Rupp said, so he turned back and shouted out. Farah flashed a thumb up. He was grateful to Rupp, “he is a great sportsman”. Rupp then told him “just get behind me” and they set off again, Farah asking himself “is the race done? Is the race done? No, no, no.” Farah explained that he had promised his daughter Rihanna a medal “and I wasn’t going to let her down”.

Facebook Twitter Pinterest Farah’s wife Tania Nell and daughter Rihanna celebrate in Rio. Photograph: Shaun Botterill/Getty Images

“If it happened with five laps to go I think the race would have been over,” Farah said. But he had time to recover. And besides, it all happened so quickly that there was hardly time for the other runners up front to realise what had happened. He was desperately worried that they would spot the chance to and accelerate away. “I was hoping the guys didn’t see me fall at the front,” he said. The three Kenyans, Tanui, Bedan Muchri, and Geoffrey Kamworor did hit the front in a bunch, but by then Farah was already up on their heels. They tried to block him off, but eventually split, and Ethiopia’s Yigram Demalesh took the race on into the final few laps.

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Virén once said that “it is the mental side which can be the deciding factor” in any race. He liked to a Finnish word, sisu, which has no exact translation in English, but which he defined as “the ability to endure and overcome any pain and challenge through mental strength”. Farah may not know it, but he showed it. His mental strength comes from his faith in his kick over the last 400m, when all the biomechanical work he has done with Alberto Salazar really starts to show. Salazar taught Farah how to increase the number of steps he takes without cutting down his long stride, which eats up two-and-a-quarter metres of track. That gives him an edge over everyone else. He knows it, and so do they.

In full flow Farah looks such a natural, but his technique has in fact been calibrated with scientific precision. He lands on the balls of his feet, places his front foot precisely beneath his knee so that he keeps his centre of balance, and quickly whips his trailing leg up towards his back to cut the distance that it has to travel before it’s ready for its next stride. That’s why Farah can fly. Tanui tried to take him on. He took the lead at the bell and kept it for much of the final lap. But Farah pulled up to him and then kicked on again coming around the last bend. He last lost a major championship race at the World Championships in 2011. They’ve been trying to find a way to beat him for five years now, and they still haven’t done it.

• This article was amended on 15 August 2016. An earlier version said the Finnish word susi could be defined as “the ability to endure and overcome any pain and challenge through mental strength”. That word is sisu.