Coroebus ended stablemate Native Trail's unbeaten run with a convincing display in the Qipco 2000 Guineas.
The 5-1 shot showed the better turn of foot in the closing stages to get the better of the 5-4 favourite. It was a one-two for trainer Charlie Appleby and owners Godolphin in the mile showpiece, worth £283,550 to the winner.
Appleby said: "It was always going to be a hard call for William to get off Native Trail to get on Coroebus but James (Doyle) is an integral part of the team, for him to have his first English Classic winner is fantastic.
"I don't think William will have any excuses, I think he was beaten by a better horse. I can see James was travelling for fun."
Buick was the first of the jockeys to commit for home on the market leader, as the horses raced on opposite sides of the 15-runner field. Coroebus found a fine mid-race change of pace to take it up and he stayed on strongly out of the dip for a three-quarter length score.
Aidan O'Brien's Luxembourg (9-2), who found the early pace a little too hot, kept on with gusto to take third. The positive showing led bookmakers Betfred to cut his price into 5-2 for the Cazoo Derby on June 4. Coroebus, last seen taking the Autumn Stakes over course and distance in October, provided Godolphin with a fourth 2,000 Guineas triumph.
Doyle described his mount's change of gear as "incredible" when returning victorious on the son of Dubawi.
"My only worry was getting left without any cover but after half a furlong I was pretty happy. He warmed into the race so easily," he said.
Buick warmed up for the Classic aboard the Charlie Hills-trained Khaadem (7-1) in the Group 3 Betfair Palace House Stakes. The six-year-old kept on gamely in the final furlong to see off the challenge of Existent (25-1) by a neck.
Buick said: “He’s got some amazing mid-race pace and especially here you’re able to nurse him into the dip and come out the other end. He’s a very talented horse.”
Alex Cole, Racing Manager to owners Jim and Fitri Hay, added: “We came back here on a retrieval mission so we’re over the moon as it’s hard to win these races."
Appleby's sole runner in the fillies' Classic on Sunday, the Qipco 1,000 Guineas, is Wild Beauty. The Frankel filly is priced at 16-1 and faces 13 rivals, including Tenebrism, unbeaten in two starts and the Jessica Harrington-trained Discoveries.
Two horses travel over from France for a shot at the huge prize, Malavath and Zellie.
Full results from Newmarket on Saturday
1.15
1 Umm Kulthum 100-30
2 Tenaya Canyon 25-1
1.50
1 Blackrod 13-2
2 Above 33-1
3 Chairmanoftheboard 33-1
4 Justanotherbottle 28-1
2.25
1 Cap Francais 22-1
2 Turntable 12-1
3 Notre Belle Bete 100-30f
3.00
1 Khaadem 7-1
2 Existent 25-1
3 Saint Lawrence 11-1
3.40
1 Coroebus 5-1
2 Native Trail 5-4f
3 Luxembourg 9-2
4.15
1 Contact 11-4f
2 Tritonic 9-2
3 Rhythmic Intent 18-1
4.50
1 King Of Time 11-10f
2 Bullet Force 14-1
5.25
1 Ingra Tor 13-2
2 Harry Three 9-1
3 Anadora 9-1
