Ambivalent sprang a minor surprise with a gutsy success in the Oxigen Environment Pretty Polly Stakes at the Curragh.
The Roger Varian-trained filly made most of the running in the hands of Johnny Murtagh and fended off all-comers to land the Group 1 spoils.
Harasiya cut out the initial pace but Ambivalent soon got her head in front as Murtagh made the most of the rail position from stall one.
After seeing off Harasiya's challenge, Ambivalent (10-1) pulled out more as the pack closed in, keeping on grimly to the line to defeat the Aidan O'Brien-trained 5-2 favourite Was by half a length.
Shirocco Star, from Hughie Morrison's stable, was third and Harasiya fourth.
The 10-furlong feature lost a little of its gloss when the ante-post favourite Alive Alive Oh was withdrawn, being reported to be in-season.
Newmarket-based Varian said: "That's great, amazing.
"It was the plan (to make the running). We've held her up in the past. She ran very well in the Middleton at York (second to Dalkala) but they didn't go very quick, and we held her up at Haydock and did they didn't go quick there either and she was keen.
"I said to Johnny she stays well so there was nothing to lose sending her forward and being positive. I was sure she'd keep going, she's very tough.
"That's my first Group 1 in Ireland and I love coming here. It was a brilliant ride from Johnny, he was very good.
"She's not straightforward, the lads did a brilliant job to make sure she was not over the top before that race - at Haydock she lost the race before that start.
"We'll enjoy today and worry about where to go after that."
Murtagh said: "Roger said she was hard and tough and to let her use her stride.
"He said they might go slow so from drawn one let her use her stride. The wind was behind which probably helped her.
"She was game in the end as they all lined up to have a go at her, but she dug deep.
"She didn't waste much energy round the back so from three out she had a good bit left."
O'Brien said of last year's Epsom Oaks winner, Was: "She ran a stormer.
"The only day she's ever got her ground was in the mile race (at the Curragh on debut) and the Oaks, we know she gets a mile and a half and she was coming home well."
O'Brien indicated an option in America could be a possibility for Was.