Cheltenham Festival's winning-most trainer Nicky Henderson opened his account at this year's meeting when Simonsig landed the odds in the Racing Post Arkle Challenge Trophy.
However, it was harder work for the 8-15 favourite than many expected as outsider Baily Green made a fight of it.
Unbeaten in two previous starts over fences, the dashing grey travelled powerfully throughout in the hands of Barry Geraghty and looked set for a comfortable success.
Despite making a jumping error heading down the back straight, the seven-year-old was still cruising heading down the hill and was left in front after Overturn blundered his way over the third-last.
There was still time for a scare for odds-on backers, though, as 33-1 shot Baily Green tracked him into the straight.
But Simonsig found enough after the final fence to seal a two-and-a-quarter-length triumph.
Geraghty said: "He rallied really well, in fairness to him."
Simonsig was already a previous Festival winner, having claimed the Neptune Investment Management Novices' Hurdle 12 months ago, but had not run over fences in public since December.
Overturn, a winner of numerous big races on the Flat and over hurdles, had won each of his first three starts over fences.
And while he went with his usual enthusiasm for a long way, Simonsig appeared to have his measure when a bad mistake stopped him in his tracks.
The most disappointing horse in the race was Willie Mullins' Arvika Ligeonniere, who travelled and jumped soundly for the first half of the contest before stopping very quickly at the top of the hill.
Geraghty said: "It was harder work than I thought.
"The ground is dead, and maybe that didn't help.
"He missed one down the back and that was unlike him. He was very good at the second-last and tight at the last.
"It didn't set the headlines as we thought he might, but he was very good."
Henderson said: "He has done well to win as he ran with the choke out the whole way.
"The first three fences they were going quick, and he was wanting to go even quicker.
"He's not short of pace. We haven't run him purposely since Christmas.
"He probably ran a bit too fresh and keen. He wasn't concentrating terribly hard on what was going on.
"He made one bad mistake. The rest of it he was just going a bit too quick for his own good.
"He's just had three runs now and there's another race in him this year, I would have thought.
"We'll give Aintree some consideration.
"He's a two-miler, but he'll learn to settle - he's got to."
Simonsig's owner Ronnie Bartlett was understandably thrilled by the result.
He said: "It's very special and it's a pleasure to have him.
"He made a mistake at the top of the hill but he got away with it.
"People were saying it was all about two horses (Simonsig and Overturn) but there were a lot of good ones in it."
Trainer Mouse Morris said of the runner-up: "He ran a great race and was just beaten by a better one on the day.
"His jumping kept him in it.
"He'll probably go to Punchestown, either there or Fairyhouse."
Overturn's trainer Donald McCain blamed the conditions after the nine-year-old could finish only fourth.
He said: "It was just the ground.
"When we saw the first race we got a bit hopeful but he's a Flat horse.
"Its testing and holding - that's not him.
"We'll go wherever the ground is now."