Estimate raised the roof at Royal Ascot by providing the Queen with victory in the Gold Cup.
Trained by Michael Stoute and ridden by Ryan Moore, the four-year-old filly become the first horse owned by a reigning monarch to win the two-and-a-half-mile showpiece.
The 7-2 favourite was challenged strongly inside the final furlong by Simenon and French raider Top Trip, but Estimate stuck her neck out gamely for a famous success.
"We've always had this race in mind, she won well" - Ryan Moore
Estimate won at the meeting last year in the Queen's Vase, returning to action this season with victory in the Sagaro Stakes, after which she was promoted towards the head of the Gold Cup market.
Despite the bookmakers fancying her chances, Stoute had always urged caution, suggesting her form did not entitle her to be favourite and that her position in the betting owed more to who owned her rather than her actual chance.
In the perfect position throughout, Moore tracked last year's winner Colour Vision into the straight before striking for home.
Simenon, twice a winner at last year's fixture, looked to be coming with a race-winning run under Johnny Murtagh for Willie Mullins but could never quite draw level with Estimate, while Top Trip tried to force his way between them.
Showing incredible guts and determination, Estimate won by a neck.
Estimate is bred to win the race being a half-sister to 1999 winner Enzeli.
Moore said: "We've always had this race in mind, she won well.
"It's fantastic to ride a winner here for the Queen and in the Gold Cup, it's very special.
"She was holding them."
Following the race, the stewards held an inquiry into two incidents of possible interference, finding in the first instance that Silvestre de Sousa had been guilty of careless riding on Top Trip, suspending him for three days.
Moore was also found guilty of careless riding and suspended for two days.
Murtagh on Simenon was ruled to have used his whip above the permitted level and in an incorrect place, being suspended for four days.