Covert Love gave Newmarket trainer Hugo Palmer his first Classic when powering home in the Irish Oaks at The Curragh.
Pat Smullen eased his mount in front of long-time leader Together Forever a furlong from home and stormed to victory by a length and three-quarters.
Covert Love (7-1) won from Jack Naylor (11-2) to take her winning run to four, with 15-8 favourite Curvy third.
"We were very confident the filly would stay. Her stamina was unbelievable. She was in serious form," said Smullen.
Together Forever roared off in front, but Smullen decided to lead the pack and it proved the right tactic as Aidan O'Brien's filly maintained the pace for a long way.
"It's great to win a Classic on your home track," added Smullen.
"All credit to Hugo. I'm privileged to work for a first-class trainer and there's more improvement in her."
"I'm to be married next Saturday so this is the last time I can ever say this is the best day of my life," said delighted trainer Palmer.
"I'm terrified I'll wake up and find myself still in my bed in Newmarket. I couldn't be more excited."