Big Orange repelled the late thrust of defending champion Order Of St George to win the Gold Cup at Royal Ascot.
Trained by Michael Bell and ridden by James Doyle in the absence of the injured Frankie Dettori, the 5/1 shot was towards the head of affairs throughout and showed incredible heart to hold the fast-finishing 5/6 favourite right on the line.
Last year's St Leger hero Harbour Law kept on well for third.
Doyle was positive from the off, disputing the early lead with Quest For More before opting to do it the hard way and attempt to make virtually all the running.
Harbour Law was also prominent through the early stages, while Ryan Moore put Order Of St George to sleep at the back of the field, giving Big Orange a healthy head start.
Doyle displayed an excellent judgement of pace from the front and was still well in control turning for home, just as Moore started to really stoke up Order Of St George - who had looked in a spot of bother on the turn for home - for his challenge.
Big Orange fended off the run of Harbour Law, before Moore delivered his mount inside the final half-furlong.
It looked as though Big Orange would be swallowed up, but he kept finding for pressure and while the pair got close in the finish, Bell's runner was on top by a short head at the line. It was another six lengths back to Harbour Law.
Doyle said: "Blimey, he's as tough as they get! Full credit to everyone. It was great to get the call-up. Unfortunately Frankie couldn't have got the injury at a worse time.
"Frankie's a real star. He called me a couple of nights ago and I was probably on the phone for about 20 minutes getting instructions and him telling me all about the horse. He was spot on.
"You can't do it without the help of everyone. Frankie said to me 'whatever you do, don't interfere with him'. He knows what speed he wants to go at and you just sit as a passenger.
"I had Frankie's voice in my head as I just eased him out and let him go to the front and the rest was history.
"He got a little bit lonely. I wish the second horse had joined me a bit earlier and I think he'd have won by further then."
Bell said: "I can't give the horse enough credit. He just puts it on the line and it's just fantastic. It was an epic race. Order Of St George is a fantastic horse ridden by a brilliant jockey.
"I can't describe the feeling of pride I have in my horse. I was just praying for the line and begging for the line to come. The horse is a superstar - he's a warrior. That's his eighth pattern win and we're extremely lucky to train him."
Winning owner Bill Gredley said: "He has been working well and is thriving. All credit must go to Michael Bell. He has done a fantastic job on him. His head lad Tyrone has looked after him and Michael's staff deserve a lot of credit. They are really good guys who have done a lot of work on him.
"We are here to take the applause but there are people behind-the-scenes who deserve to take the applause.
Aidan O'Brien said of Order Of St George: "He's run a very good race. I'm not sure where he'll go next. We'll see how he is."
An elated Laura Mongan said of Harbour Law: "I threw my hat off! He ran a cracking race. We knew he was entitled to be here. He didn't have a great start to the year but has come here 100% and he is a very nice horse - there is a lot more to come from him.
"He is so exciting. I don't know whether we will go to Goodwood or not, we will have a chat with Jim [Crowley] and the owners and see what works out.
REVIEW ALL THE ROYAL ASCOT ACTION IN THE IRISH FIELD THIS WEEKEND