The quicksilver grey, who was followed in by Monsieur Le Cure, last year's Gold Cup winner Master Oats and Val d'Alene, is a top-priced 7-4 with Corals for the Cheltenham showpiece in March.
From the moment One Man flew past Young Hustler and Merry Gale at the downhill fence on the second circuit, the race became a solo tour de force. The eight-year-old left the best in England, Ireland and France trailing in his wake as Richard Dunwoody, riding him for the first time, conjured up some springheeled leaps.
Rarely can a championship race have been won so far out in the country. And, as the pair came into the straight with the pounds 48,000 prize in their keeping bar an unimaginable fall, they were given a tremendous reception by the huge crowd, who knew they had witnessed something really special.
Desert Orchid, four times a winner of the King George at its usual venue, Kempton, was paraded before the race, and Dunwoody said in the winner's enclosure: "He would be the best I've ridden, but this fellow today wouldn't be far behind him now. He was superb at his fences. He has so much scope, but he's clever and safe with it."
The only semblance of a mistake from One Man came at the first, when he was slightly unsighted in the pack.
But by the time the field came up the hill past the stands after a circuit, Dunwoody was going so well that he had time for a chat with Adrian Maguire, on Barton Bank. He said: "I was swinging off mine, and I said to Adrian that we didn't seem to be going much of a gallop. But he didn't seem to agree."
Barton Bank, a previous King George winner, and Irish challenger Merry Gale were both pulled up. Kim Bailey was delighted with Master Oats' showing after his flop at Chepstow last time, and said: "He made a couple of mistakes, otherwise he might have been second. And he's a better horse round Cheltenham."
The race was marred by the death of Book of Music, who broke his back when he fell on the first circuit.
One Man's trainer Gordon Richards, based at Greystoke, in Cumbria, deserves the utmost credit for keeping the horse at his peak through the recent severe weather.
He said: "He was absolutely spot-on for Kempton, and we've had a nightmare since then. My all-weather gallop froze for the first time in 30 years, and all we were able to do was keep him on the move trotting in the indoor school, sometimes twice a day. He had one short canter up my hill two days ago to open his lungs, but that was it."
It was Richards' second King George, after Titus Oates 26 years ago, and it was an emotional moment for him as he lifted the handsome gold trophy aloft on behalf of One Man's owner John Hales, who is on holiday in Barbados.
The trainer holds his charge in deep affection, having acquired him, for 68,000 guineas, after the death of his old boss and mentor Arthur Stephenson three years ago. He said: "I rode many winners for old W.A. in my days as a jockey, and he pointed me at many good horses as a trainer.
"He always told me this horse would go to the top once he saw black birch. He said he had a great big heart to go with his great big feet. He was right, and I like to think he was looking down and watching today."
One Man will have one more race before the Gold Cup, probably at Cheltenham next month. Richards said: "There's better to come. I was a bit worried about his fitness today, and told Richard not to take him on too soon, to ride him like a horse having his first race of the season. But he's always best up front. That's where he enjoys life."
At the behest of the owner, Dunwoody controversially replaced Richards' stable jockey Tony Dobbin on One Man, and after yesterday's display, when horse and man were one, is likely to keep the ride. Richards said: "Tony is very good, but he's young and his time will come. And he's taken this reverse on the chin."
Right Win is 16-1 with Corals for the Champion Hurdle after his impressive victory on his jumping debut in the Tolworth (Novices') Hurdle. He now goes for the Kingwell Pattern Hurdle at Wincanton.