Duty First caused a 33-1 shock in the Dubai Duty Free Stakes when routing the opposition under Hollie Doyle at Newbury.
The Archie Watson-trained filly had shown some decent form as a juvenile, with her best performance coming when third in the Rockfel Stakes at Newmarket.
Nevertheless, she looked to have plenty to find against the likes of Simmering, Heavens Gate and the favourite Mountain Breeze.
While Mountain Breeze tried to make all before fading, the other two fancied runners never showed up at any stage.
Duty First moved into contention well over a furlong out, with the response immediate when Doyle asked her, and while Time For Sandals (14-1) gave chase she eventually lost second through her efforts.
Instead it was 40-1 chance in Hey Boo, previously unbeaten but putting up a huge career best for Jack Channon, who claimed second, three and a quarter lengths in arrears.
Watson said: “I don’t know if I was taken by surprise and I guess probably as it looked a very strong Fred Darling and you had proper Group horses in there.
“The way she has won it has probably surprised me, but the fact she has come and done something like that hasn’t really, as she has been in great order this spring.
“She can definitely go to a mile in the Guineas, she’s not in the English Guineas but I think that’s where she will run – she was actually scheduled to go to the Italian Guineas, but I don’t think that will happen now.
“I imagine after a performance like that she will go to Newmarket.
“She was still very raw when she ran in the Rockfel last year and I don’t think the undulations on the Rowley Mile will bother her, she’s also been round Goodwood and ran well there, so I’m happy. A Classic horse is what we all want.”
Doyle added: “She’s hit the line hard and I think she will improve for the step up to a mile. We’re not overly surprised, as her work at home has been good and we’ve always thought highly of her.
“She probably wasn’t quite where she needed to be last year and yet achieved more than she should have, so hopefully this is her year this year.”
Channon said of Hey Boo: “Our filly is still a big baby and George (Wood, jockey) said she travelled really sweet and he thought he had the winner covered, but she has just quickened very smartly and our filly just didn’t quite know what she was doing.
“Two runs on the all-weather is no real preparation for this type of race really, but you saw her class and potential at the end and a mile will see her in a lot better light – I wouldn’t swap her.
“She goes straight to the Guineas, she’s a high-class filly and I think she deserves her place there.”
Harry Eustace, trainer of the third-placed Time For Sandals, said: “I think we’re allowed to think about the Commonwealth Cup and her form is solid. It’s a race where fillies have done well in, funny enough, the few that have run in it, so we’ll think about that and we’ll just have to see how she trains.
“She’ll get an entry for it and that stiff six at Ascot could be ideal, but she’s a filly who could be a lot of fun.”
