James Cracknell was a 14-year-old junior at Kingston Grammar School (KGS) when headmaster Tony Creber sensed the genius that lay beneath his unassuming manner.

“You’ll be an Olympic rowing champion one day,” he told the lad. And so it proved in 2000, when he became one of the gold medallists in Britain’s coxless four.

But Mr Creber did not foresee that “Crackers ”, as he is nicknamed, would become one of Britain’s most successful athletes of all time.

Though the school launched him on a rowing career in which he garnered two Olympic golds and six world championship titles, it is now honouring him for a very different achievement. For it has named him Old Kingstonian of the Year 2009 for a very different achievement: reaching the South Pole in second place only to the experienced Norwegian team in the Amundsen Omega 3 South Pole Race.

This retraced the steps of the ill-fated Captain Scott’s expedition in 1910, and involved 10 competing teams travelling 483 miles across the toughest terrain on Earth.

James and his mates, Ben Fogle and Ed Coates, had to withstand temperatures of -50C, navigate, ski, pull 70kg sleds and tackle climbs of up to 9,300ft in the race.

Skiing 16 hours a day in such conditions took its toll on James, who developed pneumonia, frostbite and excruciating foot blisters. But he kept going and, though they had led most of the way, he and his team came in second to the Norwegians.

The current head of KGS, Sarah Fletcher, said James was an example to all the school’s pupils.

“He shows us just how much can be endured and achieved with courage and determination,” she said, announcing the award. “He is a champion rower, but not a champion skier. To battle to and reach the South Pole on skis, not far off first place and against experts in the most challenging terrain, is an extraordinary achievement, even for a twice Olympic gold medallist.”

James - who has achieved a host of other epic physical feats, including rowing the Atlantic and the Channel, swimming the Straits of Gibraltar and various running and cycling marathons, was at KGS from 1982 to 1990.

He will return to his old school in March to receive his award from the head, and talk to pupils about his race to the pole.