Three times a winner at the top level when with the irrepressible Peter Casey, he was transferred to Tony Martin, for whom his opportunities were limited due to a long-term injury.
Having looked a shadow of his former self on his return after his absence, he was brought home to be trained by Curran, son of the gelding’s owner, Stephen.
Two outings this season gave hope that further success might lie ahead for the exuberant jumper, but few can have envisaged it coming in the top grade.
Understandably, all focus in yesterday’s race was on long odds-on favourite Un De Sceaux who took his customary position at the head of affairs from flag-fall.
A brilliant winner of the Arkle at last season’s Cheltenham Festival, he opened up an advantage of some eight lengths before turning down the back, but the field, headed by Flemenstar, closed up in behind as they turned out of the backstraight.
Still in front and yet to be asked a question, the favourite took an extra stride going to the second-last fence, got into far too close, and, to the gasps of the crowd, tumbled out of contention.
The chasing Flemenstar, ridden by Andrew Lynch, had to be nimble to sidestep the faller, while Simply Ned slipped through along the inside to take the lead.
The latter, who finished third behind Twinlight in this race last year, looked all over a winner as he moved some four clear racing to the final fence.
However, he slowed going into the obstacle and, after landing on the other side, it quickly became apparent he was running on empty.
Flemenstar, whose last win came over two years ago, closed on the leader with every stride and, in the final half-furlong, got on top to win by a length, with Hidden Cyclone 20 lengths away in third.
There was carnage on the exchanges, Simply Ned being matched at 1.03 on Betfair, while the winner touched a high of 54-1.
A delighted Curran, who took his licence out in the summer and has just three horses in training, said: “I hadn’t really thought about it, but it’s great to get my first winner in a Grade 1.
“It was a long battle to get him back. He broke down badly, and it took a year of walking and trotting before he even cantered.
"It’s been a long way back, but it’s been worth it. Danny Hand rides him at home every day and has him switched off, which is a great help.”
Curran admitted the race panned out well for the 16-1 winner: “We were happy Un De Sceaux was going a good strong gallop, and the ground was heavy, which suited him. He jumps well out and, with his legs, he needs that ground now. The race worked out very well for us.
“I thought Simply Ned had the race won going to the last, but I knew our horse was fit – as fit as he had been in a long time - and he’s all heart.
“I have just three horses in training – him and two nice, young horses - but if we only had him, it’s all we’d want.”
Punchestown, at the end of next month, is a likely next step for Flemenstar but Curran added “It’s unlikely he’ll go to Cheltenham as, wherever he goes, the ground will have to be soft.”
Ruby Walsh, rider of Un De Sceaux, said: “He was fresh early on, as you’d expect on his first run back, but I thought I had him back leaving the back straight. He quickened up going to the second-last, and I thought the stride was there, but the horse didn’t. Up until that I was very happy with him.”
The bookmakers reacted to Un De Sceaux’s fall by easing him out to 7-4 for the Champion Chase at Cheltenham.