Leading Light, the 10-11 favourite, won a thrilling Gold Cup on Ladies Day at Royal Ascot on Thursday.
The colt landed the first prize of 212,662 pounds to hand Irish trainer Aidan O’Brien his sixth victory in the Group One race.
Leading Light finished a neck in front of Queen Elizabeth’s horse, 2013 winner Estimate (8-1). Outsider Missunited (40-1) was a short head away in third place.
“Your heart was in your mouth there,” O’Brien told Channel 4 television. “I thought he had a lovely position and finished well and when the race came on he was a little bit slow to react.
“I thought Joseph did well as he was just very lazy when he got there,” added the trainer in reference to his son and Leading Light’s jockey.
“We’re delighted. I’m so lucky to have the horses and to be working with the people I’m working with.”
Four-year-old Leading Light has only been beaten once since October 2012 and won the Queen’s Vase at Royal Ascot 2013 en route to victory in the St Leger.
The colt grabbed the lead late in the two mile four furlong contest.
Brown Panther, co-owned by former England and Liverpool football player Michael Owen, was fourth.
“Always when you win it’s a good race. There is no such thing as a bad winning race,” said 21-year-old Joseph O’Brien after riding his first Gold Cup winner.
“I kept a straight line all the way up the straight, Ryan (Moore on Estimate) was looking for a bit of room as he was well entitled to and I was quite entitled to keep on the run that I had.
“When we got to the front he had a little look and he just came out for a stride.”
(Writing by Josh Reich, editing by Tony Jimenez)