But as he disappears from the scene, as with the Cheshire Cat, it is his grin that will linger longest…

Since he arrived on the international scene in 1992, when he won the 5,000 and 10,000 metres double at the IAAF World Junior Championships, Gebrselassie has made at least as strong an impact off the track as on it. His excellence in competition has been unfailingly complemented by humility, affability - and that wide, dazzling smile.

Unlike the fellow Ethiopian who eventually eclipsed his track times, the current world 5,000 and 10,000m record holder Kenenisa Bekele, Gebrselassie has always seemed at ease with the media, mastering English early in his career and always responding thoughtfully to questions posed.

Personally I will long remember the time he and his perennial Kenyan rival Paul Tergat, another dignified and graceful ambassador for his sport, accorded to myself and a couple of other journalists before the 2002 London Marathon.

For three quarters of an hour, these two great champions sat and spoke about their careers, and their rivalry, in a spirit of mutual respect and with a lot of laughter round the edges.

As it turned out, neither of them won that year’s race in London. Gebrselassie, making his debut at the distance, has asked through his manager Jos Hermens for the pacemakers to reach the halfway point in 62min 30sec, which was a minute faster than any other such request in the 20-year history of the event, and more than half-a-minute inside the halfway time recorded by the then world record holder, Khalid Khannouchi.

"It's difficult to say this time, or this pace," Gebrselassie said. "But of course I think about winning the race, and I can say I am ready to do something special.”

In the end, however, he finished third, with Tergat second and Khannouchi improving his world record to 2 hours 05min 38sec.

Even for this illustrious multiple Olympic and world champion, the marathon distance required serious adjustments - a lesson more recently learned by Britain’s Mo Farah.

Gebrselassie was destined never to win in London - indeed, 2002 proved his high point, as he finished ninth four years later, in what he described with uncharacteristic severity as “the worst race of my career”, and in 2007 dropped out after 18 miles with a stitch and breathing difficulties attributed to a pollen allergy.

But what made this Ethiopian special was the way in which he kept returning to the roads and improving - to the point where he set a world record of 2:04:26 in winning the 2007 Berlin Marathon, and returned to the same city a year later to become the first man to complete the distance in under 2 hours 04min, clocking 2:03:59.

His earlier track career was marked by similar stellar performances, but also offered a full range of examples where he demonstrated his extraordinary tenacity.

It is almost 20 years since Gebrselassie produced one of the greatest flourishes in 5,000m running at the Weltklasse meeting in Zurich. I was among those who witnessed his destruction of the world record of 12:55.30 set two months earlier by Moses Kiptanui of Kenya - who himself finished up that night with a world record, in the 3,000m steeplechase.

Gebrselassie clocked 12:44.39. No one had taken such a chunk out of the 5,000m record since 1932, when Lauri Lehtinen reduced the mark of his fellow Finn, Paavo Nurmi, by 11.2sec. No one in the intervening years - not Gunder Haag, not Vladimir Kuts, not Emil Zatopek, not Kip Keino, not Ron Clarke, not Lasse Viren, not Said Aouita - had approached such a margin of that achievement.

A couple of months earlier Gebrselassie had set the 10,000m world record of 26: 43.53. That mark was surpassed by Morocco’s Salah Hissou in 1996, but on August 4, 1997, the Ethiopian reclaimed it with a time of 26:31.32, nine days before reducing his world 5,000m mark to 12:41.86.

He seemed untouchable. But nine days later, as I witnessed along with several thousand other disbelieving observers in Brussels, both his world records disappeared in the space of an hour as Kenya's Daniel Komen ran 12:39.74 for the 5,000m and then Tergat produced a 10,000m time of 26:27.85.

As Gebrselassie recalled the following year: "I said to my friend, 'This is not my day'.”

He vowed to regain both records.

In June 1998, he duly did so, running 26:22.75 in Hengelo and, 12 days later, reducing the world 5,000m record to 12:39.36.

If there was one performance which exemplified his speed, talent and tenacity it was surely his retention of the Olympic 10,000m title at the 2000 Sydney Games, where he and his great rival Tergat produced a final sprint of such ambitious intensity it seemed briefly as if the laws of physics might bend and allow both men to win.

As the finish neared, it seemed the tall Kenyan, five-times a World Cross Country champion, would exchange the silver he had won behind Gebrselassie four years earlier for gold.

But the little man behind him, teeth bared in a grimace rather than a grin, was not having it. And it was the Ethiopian who crossed first, by 0.09 - less than the margin of victory in the Sydney Olympic 100m final.

It was a truly great race, won by a truly great runner.