Banbridge overhauled long-time leader Il Est Francais at the last fence to claim a dramatic win in the King George VI Chase at Kempton.
Il Est Francais had been ahead under James Reveley for almost all of the three-mile Boxing Day showpiece, having a comfortable lead, and with two to go Banbridge was the only horse who looked likely to challenge.
At the last, the leader was less than fluid and the 7-1 chance jumped it better and raced clear for Paul Townend and trainer Joseph O'Brien.
Il Est Francais (9-2) held on for second, with L'Homme Presse (14-1) third for Charlie Deutsch and Venetia Williams.
Banbridge's participation in the King George came after a discussion in May between O'Brien, the son of champion Flat trainer Aidan, and the horse's owner Ronnie Bartlett following victory in the Champion Chase at Punchestown.
But after Il Est Francais, trained in France by Noel George and Amanda Zetterholm, had built up a lead of about 10 lengths, victory for any of the chasing pack, including Banbridge, seemed unlikely.
"I thought Il Est Francais was gone, turning for home," O'Brien told ITV Racing.
"I grew up watching races like this, so to have a runner is special and to win a race like this is dream stuff."
Townend added: "I felt I could catch Il Est Francais. I thought it was on, going to the second last.
"Stamina was a question mark, that's why I rode him like I did."
O'Brien was non-committal about the eight-year-old's plans for the rest of the season and whether the Gold Cup or the Ryanair Chase would be his Cheltenham Festival target.\
