However, having had a breathing operation after his last run, Sheehan had saved plenty for the famous hill and a good leap at the last kept him three lengths clear.

Paul Nicholls’ Saphir Du Rheu gave chase but he was three and a quarter lengths down at the line, with his stablemate Zarkandar the same distance back in third after a jolting mistake at the second-last cost him any chance of victory.

It was a first Festival success for trainer and jockey, coming at 16-1.

Greatrex said: “We’ve just won a Grade One and beat the best, so we’re here, aren’t we?”

Greatrex added: ``If you're going to break your duck (at Cheltenham), you may as well do it in a big one.

“This means everything. I was struggling with him early season, but then he went and won at Wetherby and I didn’t know what to think.

“I knew there was something wrong in the winter so we had his wind done after the Cleeve and I haven’t missed a day since then.

“I need to thank my head lad Graham who does everything with this horse.

“We knew he was spot on, you don’t come thinking you are going to win, but I knew the rest would have to be right on their game.

“I thought going to the last we had them as he wouldn’t stop.

“It’s fantastic. We’re trying to compete with the big yards and hopefully this will help.”

Sheehan said: “It’s pretty special – very, very special.

“Warren got me psyched up before the race. With fractions, you can’t get them right all the time but you can only feel what your horse is giving and he gave me an exceptional ride. His jumping was brilliant. He was very quick and did everything right.

“I was very nervous coming down the hill, I was holding on to him and wondering if I should send him on. Then I turned into the straight and he kept picking up and I was like ’where is everybody’ but when I saw the line, it meant everything.”