The 12: 1 chance Al Boum Photo, ridden by Paul Townend, was an excellent performance to help coach Willie Mullins win the Cheltenham Gold Cup for the first time.
Mullins, the festival's most successful coach, was second in the prestigious race six times.
Al Boum Photo had some worried moments when jumping. But he ran away and won two and a half lengths.
Irish challenger Anibale Fly (22-1) was second, while gray Bristol De Mai (18-1) was third.
"I can not believe it," said an emotional Townend to BBC Radio 5 Live. It means the top, and I can not believe I won it.
"I've got a nice rhythm and when it feels good, it seems so easy."
For a long time it looked as if last year's winner Native River and runner-up Might Bite would be in transition again when he headed for the field after the first lap.
Clan Des Obeaux, owned by former Manchester United coach Sir Alex Ferguson, looked like he was challenging.
But it was Al Boum Photo, one of four Mullins runners in the race and the only one who made it to the second round that looked the best.
The couple had a slight wobble at the penultimate end before they could safely overcome the final fence and fight the famous Cheltenham Hill for victory.
Townend and Al Boum Photo were at the center of a dramatic event at last year's Punchestown Festival, which overturned the jockey with a 21-day ban on dangerous riding.
While Townend was leading the chase of champion newbies, he steered the horse to the right of the last obstacle after apparently hearing a scream calling for it to be bypassed.
He collided with the runner of Finian and bounced against the white fence.