Society Rock produced an upset to win Saturday's feature race at Ascot - the Golden Jubilee Stakes.
The 25-1 winner, ridden by Pat Cosgrave, weaved his way through the field late on to go one better than last year when he came second.
Star Witness looked the likely winner leading inside the last furlong, but Society Rock trained by James Fanshawe finished strongly to clinch it.
"This horse has been working well and loved the ground," said Fanshawe.
Another outsider Monsieur Chevalier, ridden by Kieren Fallon, was beaten into second.
The victory provided Cosgrave his first Royal Ascot winner, after he rode a patient race, settling his mount towards the rear of the faster far-side group.
Bewitched was sent off the 3-1 favourite and, although she raced aggressively on the far side for a long way, the Irish challenger faded before the final two furlongs.
Fanshawe then tasted success again with
claiming the Wokingham Stakes.
"A double at Royal Ascot - it's been a brilliant day," said Fanshawe. "We have had plenty of good days, but they haven't been for a while and this is very special."
kept intact her unbeaten record with a convincing performance in the Chesham Stakes, the first race on the final day of the meeting.
Ridden by Ryan Moore, the 5-2 favourite got off to a fine start in the seven-furlong contest and was never far off the pace.
As the front-runners dropped away, Maybe was left in front and only Fort Bastion, ridden by Richard Hughes, was able to keep up with her.
O'Brien said: "We were afraid of conditions, but we thought she was a classy filly at home and she was very impressive at Naas first time out.
"When the ground changed we didn't really know what was going to happen, but we always thought she was very smart.
"She's like a lot of those very talented horses - she hits the gates very naturally and travelled very easily.
"Ryan said she got into a lovely rhythm and she was very tough at the end. I'm not sure [about her best trip]. She won her maiden over six furlongs and obviously this was seven and she got it very well.
Maybe is now the favourite for next year's 1,000 Guineas.
Await The Dawn
stormed to victory in the Hardwicke Stakes. Ridden to lead over a furlong out, he pulled clear on softer than ideal ground to romp home by three lengths from the valiant Harris Tweed.
The son of Giant's Causeway, Await The Dawn will now hope to follow in the hoofprints of his father in the Breeders' Cup Classic at Churchill Downs in November.
"I'd say he's won in spite of the ground as he's a daisy-cutter," trainer O'Brien told BBC Sport. "It's the same old story - he's got the class.
"We were hoping that he had so much class that he'd get the mile and a half and we think he's a very serious horse.
"We were always dreaming of the Breeders' Cup Classic - the dream is still alive."