Estimate provided a Royal Ascot winner for the Queen in her Diamond Jubilee year as she landed the Queen's Vase under Ryan Moore.
The Sir Michael Stoute-trained filly was the 3-1 favourite following victory in a Salisbury maiden and she responded generously to her rider's urgings in the straight.
Estimate finished off the two miles strongly to beat Ballydoyle's Athens by five lengths, with Ed De Gas third.
Estimate was taking a big step up in distance, having won her maiden over a mile and a half, but stamina looks her strong suit judged by this emphatic win.
Athens never looked likely to peg back the winner in the straight, while Ed De Gas travelled strongly for a long way to pick up minor honours.
Stoute said: "It's a great thing (to have a Royal Ascot winner for the Queen).
"We'd hoped to do it with Carlton House, but we've done it here.
"I think the whole country would have appreciated a victory for Her Majesty."
Of Estimate, Stoute added: "She's bred to stay.
"She's out of a real Aga Khan staying family with a Gold Cup winner in it and I felt after Salisbury she could be a Vase filly,.
"She's improved in her work of late and she's come and done it nicely.
"The Queen is delighted."
