Paul Moloney and Deep Purple en route for the winning line at Peterborough
Deep Purple was the surprise winner of the Peterborough Chase at Huntingdon, and had his price almost halved for the King George VI Chase on Boxing Day.
The 12-1 shot, trained in Wales by Evan Williams and ridden by Paul Moloney, beat favourite Tidal Bay into fourth.
Tartak (8-1) and Albertas Run (7-2) were second and third respectively in the feature two-and-a-half mile chase at the Cambridgeshire course.
Paddy Power made Deep Purple 12-1 from 20s for the King George at Kempton.
A number of horses found jumping a tall order in ground officially rated good to soft, and they included the Howard Johnson-trained Tidal Bay, the 2008 Arkle winner who started this race at 15-8.
He made a terrible blunder on the first circuit, and at the same fence Something Wells came down. Tartak, who was travelling ominously well, also lost his chance with a bad mistake.
Herecomesthetruth, who had set a frantic pace up front - perhaps prompting errors from those two - himself at the last when apparently set for third place.
All of that left Deep Purple to win at his leisure, though Tartak recovered to be runner-up, six lengths adrift. The well-backed Racing Demon had a poor race and never had a horse behind him.
Having seen his horse raised significantly in the weights for winning the Charlie Hall Chase at Wetherby, Deep Purple's trainer said he had not expected the eight-year-old to produce a performance like that.
Williams, the Llancarfan trainer, said: "Under a 10lb penalty I just couldn't see him winning like that in our wildest dreams.
"I thought I had him bang on for Wetherby but he seems to have improved even more. I always wanted to avoid Kauto Star this year but I suppose it makes sense to keep an eye on the King George.
"We've got a small window of possibility for him to be in such form. We're never ones to shirk a challenge and if he is OK in the next 24 to 48 hours I suspect we will end up going to Kempton."
Tom George, trainer of Tartak, also has the King George as an option for the runner-up.
He said: "Two little errors have cost him the race. I'm not a bad loser and he has shown he is a class horse. I'll have to speak to the owners but three miles on a flat track would suit him."
They would both have to do something extraordinary, however, to deny Kauto Star a fourth successive King George - with the Paul Nicholls superstar a general 8-11 chance to keep his crown.