Billesdon Brook created history when causing a 66-1 shock in the Qipco 1000 Guineas at Newmarket.
Trained by Richard Hannon, she could only manage fourth place on her first run of the season but on quicker ground she left that form way behind her.
In providing jockey Sean Levey with a first Classic success, she will go down in the record books as the biggest-priced winner of the race – though Jacqueline Quest was first past the post at the same odds in 2010, only to be disqualified.
Fillies’ Mile heroine Laurens looked the likely winner when committing for home early, but she was mowed down late by Billesdon Brook and had to make do with the runner-up spot. Happily, the 11-4 favourite, was third.
Hannon said: “It was a surprise, but there was nothing fluky about it. This is great. I knew she’d win!
“My Guineas winners aren’t terribly popular with the punters as they tend to be big prices.
“All of our Guineas winners have needed their first run – they tend to get beat in their trials. I’m just delighted for everybody at the yard and delighted for Sean.
“She’s obviously a very good filly and it’s great for her syndicate – they’ve been in the game a long time and they’ve worked hard for a day like today.”
Hannon added: “It’s great for Sean. It’s put him on the map. He was already on it but this is great. He’s there every day and works very hard.
“You are not defined by how many winners you ride or train, but by how many good ones. I’ll sleep well tonight, I think.”
On future plans, he said: “I can’t remember if I put her in the Coronation Stakes as I didn’t really see this coming.
“I think she is a miler. She travelled very well and did that great.”
Levey, who was hit with a two-day ban for using his whip above the permitted level, said: “It’s a massive shock, to be honest.
“When she ran in the Nell Gwyn she was a little bit gassy, but that was her first run and I thought she ran well to finish fourth.
“She had a lot to find with a lot of them but she was settled throughout and then found a turn of foot. I kicked on fully two furlongs out, which I thought might be a bit early, but I didn’t want to disappoint her.
“I’ve had plenty of winners and opportunities but I’ve always needed that Group One, so I’m delighted.”
Trainer Karl Burke was proud of Laurens and said: “I know she didn’t win but we can’t be disappointed.
“It’s just a shame they didn’t get the extra rain on Monday but there’s nothing we can do about that. She’s a high-class filly and PJ (McDonald) gave her an excellent ride.
“I thought we came with a great chance and the winner wasn’t one we were frightened of but we’ve been second in a Guineas and have a lot to look forward to.
“She’ll come on (for the run) and I imagine it will be the Prix de Diane now. She’s in the Irish Guineas but I imagine it will be France.”
John Dance, owner of Laurens, said: “The first thing PJ said was, ‘We’ll go to France over 10 furlongs (for the Prix de Diane) and she’ll gallop them into the ground’.
“It’s been a dream since day one with her. Just to win a Listed race was great but she’s won a Group One and been second in a Classic.
“If she’d have won I think I’d have been in tears and on the floor. I’m just incredibly proud.”
Happily’s trainer Aidan O’Brien said: “She will probably go to the Irish Guineas now. Ryan (Moore) was very happy with her.”