The Marcus Tregoning-trained Boom And Bust led the field almost from start to finish to win the Totesport Mile at Glorious Goodwood.
Jockey Hayley Turner moved her horse, priced at 22-1, to the front early on and held off the challenge of Proponent to win the handicap by a neck.
Pintura, priced at 18-1, was third with 14-1 shot Sooraah finishing fourth.
"I'm thrilled, it was a very good ride by Hayley. Boom And Bust has surprised me," said Tregoning.
Turner added that she was confident of letting the Irish horse head the field.
"Being drawn in number one is a huge advantage," she said. "He enjoys bowling along in front because he settles well. You have to be decisive."
Green Destiny, the 15-8 favourite, finished well down the 20-horse field. Only two favourites have won in 25 runnings of the race.
Meanwhile, Harbour Watch is now unbeaten in three races after winning the Richmond Stakes.
The evens favourite, trained by Richard Hannon, pulled clear of the field in the closing stages despite being carried across the track by Bogart in the final furlong.
Richard Hughes kept his ride steady which won by two-and-a-quarter lengths from Bannock with Caspar Netscher in third.
Bookmakers shortened Harbour Watch's odds for the 2000 Guineas from 16-1 to 10-1 favourite.
Saturday's feature race is the Nassau Stakes with the Sir Henry Cecil-trained Midday looking to win the race for a third successive year.