Johanna Walsh proved an able deputy for Joseph O'Brien by landing the Irish Oaks (G1) July 18 at the Curragh.
Her trainer had suffered a blow early in the day when he was forced to scratch Epsom Oaks (G1) winner and favorite Thundering On because she was reportedly off her feed.
But apparent second-string Johanna Walsh put a smile back on his face by landing the prize impressively.
The winner was having her first run in group 1 company, and only her fifth overall, having been caught close to home in the Ribblesdale Stakes (G2) at Royal Ascot last month.
Dylan Browne McMonagle sent the 7-2 shot to the front early in the straight and she never looked like being caught.
Runner-up Inis Mor was 4 lengths adrift at the line, with another three-quarters of a length back to Sparan Nua in third.
"That was unreal," the winning jockey said. "It was very straightforward from the get go. I was always in control of the race.
"She's a filly with a lot of gears and when I pushed the button she put the race to be within a couple of strides and she powered away. She wasn't a bad substitute."
The 9-4 favorite Earth Shot, who finished only sixth, had beaten Johanna Walsh at Ascot but McMonagle said: "I thought mine was probably a little bit better than that with the way the race panned out.
"She was unbelievable today, it was push-button stuff. Thundering On is obviously a little bit special, it's hard to know what she would have done the way this one performed, but thankfully it worked out."
