Who knows how many people are already claiming They Were There when Mo Farah secured his second gold of the London 2012 Games in the Olympic Stadium? Already, no doubt, it will be in excess of 80,000, the stadium capacity.

As it was, the noise generated at the end of that 5,000 metres race, when the Somali-born runner rounded the top bend with a pack of five rivals at his heels and kept them all there for the length of the straight, was so great that one's ears – yes, I was there, honestly – began to ring.

And then, as Farah entered the final 25m, the atmosphere became so tumultuous that for a few seconds you couldn't properly hear anything. It was like the amp in Spinal Tap being turned up to volume 11.

The expression on Farah's face as he crossed the line was not one of disbelief, so much as extreme belief. "Two medals – who would have thought it?" was his reaction after completing the 10,000/5,000m double. But the answer was: him. And the answer was also: Alberto Salazar.

Farah's decision to up sticks from London and join the former New York Marathon winner in Oregon, taking his wife and stepdaughter with him, was the last in a series of shifts which have enabled him to maximise his rich talent. The double Olympic champion doesn't give off the driven vibe of, say, Paula Radcliffe or Seb Coe, but in his way he has been just as calculating and single-minded in reaching his present position as one of the nation's cherished sporting performers.

Mo Farah celebrates as he crosses the finish line to win gold ahead of Dejen Gebremeskel of Ethiopia and Thomas Longosiwa of Kenya in the London 2012 men's 5,000m final

At 29, Farah has finally arrive at the position that was being forecast for him more than a decade ago when he started to produce stand-out performances after he had made the first and most important shift of his entire life in 1993 by moving from his native country, a war-torn Somalia, to join his father, who was already living in Britain.

I first spoke to Farah early in 2000 – although the immediate circumstances were unpromising. Young Mo was waiting at a bus-stop with his school mates, and as I strained to hear his quiet voice on the phone the task suddenly became more vexed as a bus arrived and everybody piled on.

Against a background of noise which suggested his fellow pupils were systematically destroying their means of transport, Farah recalled how his knowledge of the English language was so limited when he arrived in Hounslow from Mogadishu that he got into a fight on his first day at school.

Mo Farah in action during the 2001 Aqua Pura International meeting held at Loughborough University

He also remembered how, during his first cross-country race for the Borough of Hounslow club, he had lost the chance of winning when he took a wrong turning, baffled by the signs on the course.

But that talented, if confused young athlete has now very definitely found his way – and cross-country has been one of the key means of reaching the position in which he now finds himself.

In December 2006, I saw him earn his first significant gold after six consecutive silver medals as he took the European Cross-Country title at San Giorgio su Legnano.

Earlier that year Farah had had a reward for an enterprising decision which prefigured his shift to Oregon when he threw in his lot with the Kenyan athletes who used Teddington as their European training base. After spending months living the dedicated and frugal life they followed – eating carbohydrate-rich ugali, watching television in the lounge during downtime, and running, running, running – he produced the second fastest 5,000m time by a Briton, 13min 09.40sec.

Clearly, when he took to the cross-country course in Italy he was in a position to win. And, just as Radcliffe had done in her career, which hit the top level after she had become world cross-country champion in 2001, he followed up a breakthrough on the grass with one on the track.

Later in 2006 he missed winning the European 5,000m title by just 0.09. Four years later he returned to the Europeans in Barcelona and completed a 5,000/10,000m double. He was properly in business.

Mo Farah with his 2010 European Athletics Championships 5,000m gold medal

Farah, with his dazzling smile and amiable manner, has been the Changingman of British athletics – but unlike the character in Paul Weller's song, his ambitions have not been built on shifting sand.

He has never been what you would call risk-averse, which has usually been a strength. Although David Bedford, the former race director of the Virgin London Marathon, likes to recall the time he managed to persuade Farah to have a night out with him and others in 2006, at the end of which the runner decided to take off all his clothes and jump into the Thames off Kingston Bridge.

"I don't have as many nights out nowadays," Farah told me. "But if I have something to celebrate in the future, anything can happen."

Such revels are unlikely to figure in his 2012 celebrations, however, as he and his wife look forward to the imminent birth of twin girls.

Had circumstances been different, Farah might have been giving the Netherlands cause for celebration this Olympic year. When he emigrated, the original plan was for him to come to Britain and then go on to Holland to live with his grandmother. But he liked Britain so much that he stayed. Britain is glad.

Mike Rowbottom, one of Britain's most talented sportswriters, has covered the past five Summer and four Winter Olympics for The Independent. Previously he has worked for the Daily Mail, The Times, The Observer, the Sunday Correspondent and The Guardian. He is now chief feature writer for insidethegames.