Ridden by Paddy Brennan and trained by Nigel Twiston-Davies, Imperial Commander pulled away at the last fence to win the top race of the Cheltenham Festival and end three years of domination by Paul Nicholls, trainer of stablemates Kauto Star and Denman. Kauto Star won the race in 2007 and 2009 and Denman won it two years ago.
The 7-1 shot Imperial Commander won his sixth of 10 races at Cheltenham but the failure of Kauto Star to make it three wins in four races was a major surprise.
With Denman making a move at the front, jockey Ruby Walsh tried to get Kauto Star to respond as the field reached the final turn but the horse, back in fifth place, clipped the fence and went down. It was his second mistake, almost falling at another fence before the halfway stage of the 3-mile (5.2 kilometer) race for top chasers.
"You can't make a mistake like that with horses of the caliber of Imperial Commander and Denman lying in front of you," said Walsh, whose mount was the 8-11 favorite having won the King George VI Chase at Kempton Park for the fourth year in a row in December.
"You take your position and you're always struggling then but I was fighting a lost cause and he fell." Denman failed to get clear of Imperial Commander as Brennan's 9-year-old stayed with him before pulling away to win convincingly.
Denman beat Kauto Star in 2008 but lost to his stablemate last year. He finished second at odds of 4-1 and last year's Grand National winner, Mon Mome, was a 50-1 third of the 11 starters.
"It's by far the best day of my life. I'm speechless," said Brennan. "It was a dream the whole way.
"I've just got to take time to thank my boss (Twiston-Davies). He's the best boss ever. He's produced two horses this week (Imperial Commander and Champion Hurdle runner up Khyber Kim) and I just had to steer them." Brennan and Twiston-Davies also teamed up to capture the final race of the meeting when Pigeon Island won the Johnny Henderson Grand Annual Chase.
To complete a memorable day for Twiston-Davies, his son Sam led from start to finish to win the Christie's Foxhunter Chase for amateur riders. He was riding Baby Run, a horse trained by his father.
"To be dreadfully honest it would have to be the Foxhunter," Nigel Twiston-Davies said when asked which performance he preferred. "I was hugely proud of Sam and he rode a beautiful race.
"It's been a hell of a 40 minutes. Maybe I'll die soon! We'll enjoy it and I'm very excited." Walsh still ended the four-day meet as the Festival's all-time most successful jockey with 27 winners and his younger sister, Katy Walsh, rode two.
Riding 20-1 shot Thousand Stars, she won the Vincent O'Brien County Handicap Hurdle by three lengths, having also won on Poker de Sivola in Wednesday's National Hunt Chase.
Kauto Star's failure to win was also a big victory for the bookmakers who estimated profits of 60 million pounds ($90 million) because so many favorites flopped at the meet.
"It was a result beyond our wildest dreams," said David Williams of Ladbrokes. "The cheers for Imperial Commander came from the bookies and we roared him up the Cheltenham hill.
"The gamble on Kauto Star was colossal. Had he won we'd have handed back all the cash we made earlier in the week.
Getting the big two beaten was nothing short of superb."