Haydock specialist Bristol De Mai got the better of Cheltenham Gold Cup winner Native River and runner-up Might Bite to land the Betfair Chase for the second year in a row.
The Nigel Twiston-Davies-trained horse, ridden by Daryl Jacob, claimed an easy victory in last year's race at Haydock.
Despite that, most of the interest going into this year's race had surrounded Native River and Might Bite.
But the 13-2 winner beat Native River into second with Thistlecrack third.
It was the fourth win out of four runs at the Merseyside track for the seven-year-old grey, who had a wind operation last winter and was second behind Might Bite in the Betway Bowl Chase at Aintree in April on his return.
This time, Jacob brought him to the head of the field from the start but the other four runners were never too far away.
Turning for home, all were still in with a chance of winning but Bristol De Mai jumped into a decisive lead with two fences to go and started to extend his advantage to win by four lengths.
The disappointment of the race was the evens favourite Might Bite, who weakened into last place.
'He's difficult to keep right'
Afterwards, Jacob said that the Twiston-Davies yard had always believed in the winner.
"Everybody was building this up as a two-horse race, but our camp had different ideas," he said.
"It obviously was a disadvantage it not being soft ground, but at this track, there's something about it he just loves and he feels a lot better.
"They were big fences and took some jumping. I got him into a lovely rhythm. He jumped super and you needed to jump today to win and that's exactly what this lad did."
Twiston-Davies added: "He wins everywhere when he's right. He's difficult to keep right.
"First and second time out last season he was superb, then he started getting his aches and pains and taking a few lame steps. Hopefully second time out this year will be at Kempton and we'll give them a hard time there.
"We don't mind being the underdog. We were discussing on the way up here how it reminded us of Imperial Commander taking on Kauto Star and Denman in the Gold Cup. We were totally the underdog and then you go and stuff them like that!
"What we've got to do is bring this horse fit and keep him right."
BBC horse racing correspondent Cornelius Lysaght
Much of the talk in the build-up was of the Haydock course potentially favouring Might Bite, but it was an established track specialist Bristol De Mai who made it four out of four, beating Native River, who kept on for second.
The winner bossed this for much of the way, dispelling suggestions he requires soft going.
Thistlecrack ran a terrific race in third, but the comprehensive defeat of Might Bite - blamed on his jumping of what the jockey called the "very upright and big fences" and a lack of fitness - is the top line. Work to regain the slickness of his jumping will now follow.