Champ came from an impossible position to collar Minella Indo in the dying strides and win the RSA Insurance Novices' Chase at Cheltenham.
The Nicky Henderson-trained eight-year-old - named after 20-time champion jockey Sir Anthony McCoy - made several mistakes throughout the race, including at the water jump, and looked to have a mountain to climb turning for home as pace-setters Allaho and Minella Indo forged clear at the foot of the hill.
Rachael Blackmore kicked on aboard the Henry De Bromhead-trained Minella Indo but he got in close to the last and then began to idle which appeared to reopen the door for Allaho, who was plugging on bravely for Paul Townend.
But from the clouds Champ, who was around 10 lengths down at the final fence, was finishing best of all under Barry Geraghty and the 4/1 chance emerged in the final strides between his chief market rivals to win going away by a length.
Henderson said: "It didn't look very likely to happen, did it? It looked like he was going to be an honourable third - I was watching the front two and all of a sudden he appeared in the picture. I was thinking, 'how has he got here?'
"He was 100/1 at the second-last and what price was he at the last? We had the Might Bite thing in this race a few years ago, so you'd have to say it's been a strange race for me."
He went on: "This is the first time he's been back to three miles since Aintree last year. The fall here last time (New Year's Day) rather upset plans as I didn't want to run him again, and actually as it turned out we couldn't run him again because there was nowhere to go.
"We've done a lot of schooling with him at home, Barry has been over a few times and Nico (de Boinville) has done a lot of work on him as well - he's a great schooling jockey."
Henderson added: "Let's hope we all get there."
Geraghty said: "This is a great race. Any of the Grade Ones are special at the Festival. You long for them. Nico has done a lot of work schooling him over poles with Nicky. They've done a lot of hard work to get him where he is.
"I knew when I'm committed him going to the last the two in front hadn't jumped it brilliantly. Then once he was within a few lengths of them he picked up well.
"I thought I had no chance jumping the last, but three strides later I was starting to smell the money."
Henry de Bromhead said of Minella Indo: "He ran a cracker and I'm delighted with him. Unfortunately it was a bit of shame what happened at the last, but fair play to Barry who came through and nabbed us on the line.
"Possibly (mistake at the last has cost us), but that is not for me to say, who knows, it definitely didn't help us. We are delighted with that, just gutted we didn't win.
"He is a lovely horse that stays well and hopefully he is a horse that will be back here for a few more years. He has only had three runs, so possibly we might head to Punchestown for the three-mile novice there."
Willie Mullins added of Allaho: "The two horses in front probably just took it out of each other and Barry Geraghty is riding out of his skin. Both horses were tired at that stage (the last).
"He missed one down the back and second-last, but in a three-mile chase there will always be a few down the line. I had a word with Paul Townend and he said he would be better off at that trip on better ground."