Barney Roy floored the odds-on favourite Churchill in the Group I St James's Palace Stakes (1m) to give Godolphin two feature winners on the opening day at Royal Ascot.
Settled in fourth by James Doyle as his saddle slipped and Rivet went forward to lead at a solid clip, Barney Roy was brought to challenge in the home straight with Churchill stalking.
Lancaster Bomber was holding Thunder Snow two furlongs out with Barney Roy (5/2) making gradual headway wide out, finishing best of all to defeat Lancaster Bomber (12/1) by one length with Thunder Snow (6/1) a head away third.
Churchill (1/2 fav) was beaten for the first time and finished a lacklustre 3 1/4-lengths behind Thunder Snow in fourth place, the trip completed in 1:37.22.
Ironically Lancaster Bomber is a half-brother to Excelebration, the sire of Barney Roy.
Barney Roy finished runner-up to Churchill in the 2000 Guineas at Newmarket last month and trainer Richard Hannon told ITV Racing he was a worried man early in the race.
"I thought he was off the bridle a bit early and I was a little worried that he was going to run a moderate race and finish fourth, but I've got a lot of confidence in this horse and I'm delighted," Hannon said.
"I was confident he'd run his race, not confident he'd win - I just wanted to give him the chance to prove that, as I don't think he got that chance in the Guineas.
A son of shuttle-sire Excelebration, Hannon hinted he may step Barney Roy up in trip and tackle the older horses.
"He's in the Eclipse, he's in the Arc. He takes time to get there but he picked up well, he's a very relaxed horse and was only having his fourth run, so to beat the Guineas winner is great." Hannon said.
Aidan O'Brien was gracious in defeat.
"He (Churchill) ran well. It's a very hot day and maybe the heat didn't help - he just didn't pick up for some reason," O'Brien said.
"Lancaster Bomber ran very well - Churchill is usually able to pick up Lancaster but he just didn't today."
