I Am Maximus lunged late to claim victory in the BoyleSports Irish Grand National at Fairyhouse.
The seven-year-old was an 8-1 chance in the three-mile-five-furlong feature for the all-conquering Willie Mullins and Paul Townend.
Ridden patiently in among the field of 27, the JP McManus-owned gelding looked set to finish out of the placings - but came to the fore as contenders dropped away and he was ridden to get into contention over the penultimate fence.
Over the last he jumped his way into third place and then battled past long-time leader Defi Bleu and Gevrey to prevail by a length.
Townend said: "It was looking unlikely for a long way. I just tried to get him back popping.
"He was too slow jumping down the inside. I wanted to keep horses outside of me but it cut me out of the race so I had to let him go left and bank on one at the last.
"This is a very special race. It's huge to win this. You need so much luck. I finished second here a few years back (on Away We Go in 2013) and my record besides that wasn't great.
"I thought Gaillard Du Mesnil was my best chance in it last year and he ran well to finish third. I'm very fortunate that this lad popped up and that it worked out in the end."
David Casey, assistant to to Mullins, added: "It was absolutely unbelievable. I don't have the words, I thought it was absolutely brilliant.
"We know how good a rider Paul is anyway, I didn't think he could better Galopin Des Champs from Cheltenham but I thought that was amazing.
"He wasn't travelling, he didn't seem to be enjoying it down the inside in the crowd. Paul just kept persevering, kept galvanising and kept saving and kept him jumping.
"He has his quirks and I thought it was an unbelievable ride.
"He does idle a little bit when he gets to the front and he does jump a little bit left. Paul was brilliant and the horse obviously had the ability to go and do it as well."
Earlier on Easter Monday, Asterion Forlonge denied Monkfish a dream return to action when winning the Rathbarry & Glenview Studs Hurdle at Fairyhouse.
The enigmatic winner was running over hurdles for the second time since pausing a chasing career that brought about mixed fortunes with some good performances but also several falls.
Monkfish, also trained by Willie Mullins, had been absent from the track for nearly two years due to injury but was a very highly regarded novice chaser prior to that.
Asterion Forlonge was the 11-8 favourite under Paul Townend as Monkfish went off at 11-4 and was ridden at the rear of the field by Danny Mullins.
Monkfish gave chase after the last fence and was closing as the line approached, but could not pass Asterion Forlonge and missed out by half a length.