Mo Farah's momentum a result of ferocious training
By Tom Fordyce BBC chief sports writer at the Olympic Stadium
Four weeks ago at Crystal Palace, in a cold, empty stadium long since deserted by the crowds who had earlier watched him win a Diamond League 5,000m race, Mo Farah stepped back out onto the track and once again pulled on his running spikes.
It was closing in on midnight, the lights low, the only people left in there were his coach Alberto Salazar, training partner Dathan Ritzenhein and a few of us journos filing late stories.
As we watched on from the dark stands, Salazar poised on the infield with stopwatch and clipboard, Farah and Ritzenhein threw themselves into a brutal session - a 3,000m time trial, a brief recovery and then four lots of 200m sprints, each completed in exactly 26 seconds and separated only by a 200m jog.
Farah powers to 10,000m gold
What was it Muhammad Ali said? "The fight is won or lost far away from witnesses - behind the lines, in the gym, and out there on the road, long before I dance under those lights."
Farah shares more than Olympic gold with the great man. Here in London's Olympic Stadium, almost exactly a week after his 10,000m triumph provided a memorable crescendo to Britain's Super Saturday, the harvest of that cruel regime bore the most beautiful fruit.
Dance under the lights Farah did. Set against almost unreal ferment and cacophony inside the Olympic Stadium, his bug-eyed, teeth-gritted sprint down the home straight to 5,000m gold was a fitting final act to a fortnight like no other.
No Briton has ever won an Olympic distance gold before these Games, let alone two. No Briton has ever won an athletics gold in an atmosphere like this, not even Jess Ennis and Greg Rutherford and Mo himself in that dizzy 46-minute gold-rush seven days ago.
Farah collects his second gold medal
Britain's best in an Olympic 5,000m final before this was a solitary silver, to Gordon Pirie back in 1956, and the bronze medals of Ian Stewart, Derek Ibbotson and George Hutson, all of them dating back 40 years or more.
Only six other men have achieved a distance double at the same Olympics, and each remains an icon - Zatopek, Viren, Bekele; Kuts, Kolehmainen, Yifter.
What makes Farah's achievement all the more laudable is not just his ability to get over the physical lows and emotional highs of that first victory, won in his home city at its home Olympics, but the backstory that brought him to this point.
Four years ago in Beijing, he failed to even get through the heats of this event.
Sixteen years further back, on his first day at school in the city having arrived as a refugee from Somalia, he tried both the English phrases his father had taught him - "where is the toilet?" and "come on then" - had the misfortune to say the wrong one to the wrong kid and took a beating.
Certain key individuals have helped guide him from that inauspicious start to this special night.
Steve Cram BBC athletics commentator
"The place erupts. My words cannot do justice to how I feel. Have you ever seen anything like that? Have you ever seen a man with so much confidence in his own ability?
"He almost teased them at times, he was tested to the full and came up with the answers. British athletics is so lucky to have one of the greatest distance runners the world has ever seen."
There is Alan Watkinson, the PE teacher who first encouraged the teenage Farah to swap football for athletics; Paula Radcliffe, whose financial support enabled him to pay for the driving lessons that meant he could get to training sessions; Alan Storey, his coach at St Mary's College in Twickenham; Ricky Simms, the agent who first suggested he should house-share with a group of elite Kenyan athletes living together near Bushy Park in south-west London, and Steve Cram, whose middle-distance races Farah admits to watching obsessively on YouTube.
All were at Farah's wedding two summers ago, and all were celebrating wildly as he held off Ethiopia's Dejen Gebremeskel and Kenya's Thomas Longosiwa in the final frantic metres on Saturday night.
There were bumps along the way. Watkinson had to bribe the 13-year-old Farah with the offer of an Arsenal shirt to get him to run cross country rather than play right-back for Brentham United; Storey had to issue stern warnings when the 21-year-old was caught jumping naked into the River Thames from Kingston Bridge.
The final key ingredient was Salazar - bringing to the now 29-year-old cutting-edge sports science, relentless excellence in training and rock-solid confidence for nights like these when other runners turn to tactical jelly.
Usain Bolt on why he and Mo Farah traded celebrations
"What Mo's rivals can't do is wrest control of the race from him when it matters," says Cram, who called Farah home on BBC television.
"We know what Mo wants to do: four laps to go he will move closer to the front, three laps to go he will be very close to the front, and with 600m to go he has to be at the front. He positions himself to make it happen.
"All his rivals know that. There are things they could do to try to stop him - go harder earlier, rough him up, try to block him. They don't, because he retains that control. They let him dictate because of what he has now done."
Farah celebrated first with the partisan crowd, then with his family, then with the other great star of the evening.
There was a valedictory lap draped in his country's flag, a hug for step-daughter Rihanna and a kiss for wife Tania, who will shortly give birth to their twin daughters. Perhaps they should call them Five and Ten.
Jamaica smash record to win relay gold
Then, once the gold medal had been hung round his neck and the anthem bellowed out by the beaming 80,000, Usain came to join the party.
Bolt is the greatest global icon of these Olympics, his anchor leg in the Jamaican world record-breaking sprint relay earlier in the evening bringing his own collection of golds to a remarkable six.
In Farah he recognises his British counterpart.
Bolt has the Lightning Bolt, Farah the Mobot. Bolt celebrated his 200m gold with 10 impromptu press-ups, Farah paid tribute with 10 sit-ups of his own.
The two are even managed by the same man, which makes Ricky Simms the third happiest man in London this weekend.
On Saturday night they first aped each other - Bolt Moboting as he received his medal, Farah pulling the Lightning Bolt as he posed with his - and then stood together, bathed in photographers' flashes and giddy adoration rolling down from the stands.
Two men, two historic doubles, one unforgettable night.