American trainer Wesley Ward lit up the final day of Royal Ascot when he saddled Undrafted to a pulsating victory in the feature race, the STG525,000 ($A1.07 million) Diamond Jubilee Stakes over 1200m.

Under a finely-judged ride from Frankie Dettori, Undrafted swooped late and fast to collar Brazen Beau, the Australian-trained favourite, in the dying strides.

The outcome marked a significant change of fortunes for the international challenge, which has largely underperformed throughout the week.

For Ward, however, it was a second winner after Acapulco's triumph in the Queen Mary Stakes on Wednesday.

Ward was overcome with emotion afterwards. He spent the previous night in nearby Frimley Hospital after his daughter, Denae, became ill with Bell's palsy.

But the pair were both on hand to witness what Ward described as "certainly the biggest race I have ever won."

Hugging Denae, Ward said: "She was very unwell but we are here today to enjoy this special moment. I can't tell you what this means."

He later described Dettori's ride in glowing terms.

"Frankie's got the touch," Ward said. "He's magical, and he showed that today."

It was Dettori's third winner of a week in which his renaissance continued apace.

Runner-up Brazen Beau was left isolated through the race when jockey Craig Williams chose to keep his mount away from the main pack.

He looked like winning until Dettori overhauled him in the dying strides.

Earlier, Michael Stoute won the Hardwicke Stakes for the ninth time in his career -- but not in the manner expected.

Stoute saddled three of the eight runners, among them last year's winner Telescope, who started a warm favourite.

But Telescope faded quickly as stablemate Snow Sky, who made all the running under Pat Smullen, galloped to a resounding victory from Eagle Top and Postponed.

Victory brought welcome relief for Stoute in a week when three of his horses suffered injuries.

Stravagante, who pulled up lame on Friday's King Edward VII Stakes, was euthanised on Friday night after veterinary surgeons in Newmarket were unable to save him.

"The horse surprised me a bit. He showed a fine turn of foot off the home bend and that won him the race," Stoute reflected after Snow Sky's triumph.

Eoghan O'Neill and Italian jockey Christian Demuro teamed up to nail their first Royal Ascot winner when Suits You fought hard to fend off Ballydoyle in the Chesham Stakes.

Of Irish descent, O'Neill moved his training operation from Britain to France five years ago to take advantage of better prize-money in that country..

After four days when the sun shined on Ryan Moore, Saturday's rains marked a turn in the tide for the man who ended the week riding a post-war record of nine winners.

Moore was beaten on a string of fancied mounts, two of them for Irish handler Aidan O'Brien, who nevertheless closed the week as the meeting's leading trainer with five winners.

The day belonged instead to Ward, who travelled back to the US having landed his sixth Royal Ascot winner in as many years since his inaugural visit in 2009.