Cyrname beat favourite Altior to win the Christy 1965 Chase at Ascot.
The 5-2 second favourite, ridden by Harry Cobden and trained by Paul Nicholls, led the near two-and-three-quarter-mile race from start to finish.
Unbeaten Altior (1-3) was unable to respond when Cyrname made a run for home with three fences remaining.
The other runner, Solomon Grey, trained by Dan Skelton and ridden by Harry Skelton, trailed in the opening stages as the head-to-head unfolded.
The meeting between Cyrname and Altior was one of the most hotly anticipated showdowns in recent memory, likened to the classic rivalry between Kauto Star and Denman.
Altior, ridden by Nico de Boinville and trained by Nicky Henderson, had been heavily backed, with punters expecting the nine-year-old to make it 15 wins from 15.
Unbeaten Altior usually takes command from the front but, after stepping up to a new longer distance, was not allowed to do that by seven-year-old Cyrname, who then turned that advantage into victory with a devastating late burst.
"I am absolutely delighted. To be honest, I was disappointed halfway round as I was thinking he wasn't travelling as well as he should have been. But we got the job done," Cobden said.
"I could hear him (Altior) every step of the way, which is why I wanted to stride on down the back and outstay him, which is what we have done really."
The win was another notable piece of history in a race that already has big names such as Wayward Lad (1981), Deep Sensation (1992) and Master Minded (2010-2011) on its roll of honour.
This first encounter could be the start of a rivalry between Cyrname and Altior that could take them both to National Hunt's Christmas showpiece, the King George VI Chase at Kempton.
Thrilling duel at Haydock
The Betfair Chase at Haydock produced the kind of duel that had been expected at Ascot, with 5-4 joint favourites Lostintranslation and Bristol De Mai going head-to-head down the final straight.
Bristol De Mai, trained by Nigel Twiston-Davies and ridden by Daryl Jacob, began stronger, with the eight-year-old looking for back-to-back wins in the race.
But it was Lostintranslation, a year younger, that eventually seized the initiative to win by a length following a thrilling sprint finish.
Jockey Robbie Power held his nerve, tracking the four-strong pack from the back of the field before making a decisive late move to hand trainer Colin Tizzard a fourth victory in the race following three previous wins with Cue Card.
Cornelius Lysaght, BBC racing correspondent:
It sounds like Team Altior quite fancies another crack at Cyrname in the King George.
It certainly hasn't been ruled out, with the hope there that the horse might turn around the result over the three miles on the flatter track at Kempton on Boxing Day when conditions might well not be so soft.
There would be an element of bravery about that: many less bold might return now to two miles, the distance at which Altior has excelled.
One small blunder apart, Cyrname jumped superbly and you felt he was in command throughout.
Enthusiastic pre-race chat about Lostintranslation certainly wasn't lost in translation: he positively burst into the big time with a fine display of jumping and galloping to see off a right old street fighter in Bristol De Mai.
There was everything to play for at the second last, but as the first and second drew miles clear of Frodon in third, the winner got away best from the final fence and was always holding on.
There's talk of Cyrname and Altior having a re-match in the King George though, based on this, Lostintranslation may be the one that rules.