A wind operation had kept the six-year-old out of action for 160 days, but he shrugged off any race-rustiness in style.
Double Treasure made a gallant effort to lead all the way, but was headed between the last two flights by Secret Investor (5-1), who went on to score by two lengths.
The first two pulled 20 lengths clear of Gosheven in third place.
“He struggled with his wind last year so we did his palate, no more than that,” Nicholls told At The Races.
“It just made a bit of a difference to him. He’s so much more improved this season. For whatever reason, he seems likes a different horse.
“We thought he’d go OK. Just because he had a wind op we thought he was a little bit behind and he might improve. All in all, that was a much-improved performance.
“He tanked really well. He maybe got a bit tired late on, but that will put him right.
“He’s already been schooling over fences and that is what he’ll do next.
“He’s a proper horse and that’s the first time we’ve seen him do what we thought he was capable of doing. That was pleasing.”
Cobden completed a double when guiding Colin Tizzard’s Kings Lad (8-1) to victory in the Gent Transport & Warehousing Veterans’ Handicap Chase, and made it a treble on the Nicholls-trained McFabulous (13-2) in the concluding bumper.
Tizzard was doubling up after Drinks Interval (10-1) gave Richard Johnson his 99th winner of the campaign in the Istadia Outdoor LED Screens Supports Racing Novices’ Chase.