He won three times last year, overhauling the leaders from behind on each occasion.
This week he led from start to finish, but after a third-round six-under-par 65 had him seemingly on cruise control he only had a two-hole winning margin over Yorkshire champion Sam Rook, of Lindrick.
This was after drama at the 17th where – having led by six standing on the tee – he racked up a triple bogey seven for the second time in the event, having done likewise in round one.
Rook birdied the hole to exacerbate the damage, but both bogeyed the last for Thornton (71 73 65 74) to edge Rook (71 74 71 69) and finish as the only man under par for the four rounds.
“I wasn’t nervous until I stuck one out of bounds at 17 and then I started to feel it a little bit,” said Thornton.
“In the afternoon I was playing steady until the last couple of holes. I tried not to think about being defensive. I was just trying still to make as many birdies as I could even though I knew I had quite a lead.
“I tried to keep my head off that, but when you’re leading somewhere in your head you’re thinking about what they (rivals) are doing as well and then you do, almost subconsciously, start to get a bit defensive.”
He almost played the wrong ball at the 16th having forgotten playing partner Rook had played a provisional. Fortunately, after measuring the distance to the hole, he was preparing to play his shot when he realised the ball had slightly different marking to his own.
Thornton was quick to praise his coach Steve Robinson as well as Selby professional Nick Ludwell, who has proved a useful source of advice on tournament play.
Carris Trophy holder Barclay Brown, of Hallamshire, shot 76 71 68 77 to make it three Yorkshire players inside the top five.
Thornton’s victory, which kept the title in Yorkshire hands after successive victories from Masham’s Dan Brown and Malton & Norton’s David Hague, was his first for 18 months.
He feels it was the reward for a lot of intensive practice he put in during the fortnight leading up to heading for Alwoodley.
“The last few weeks I’ve been working really hard on my game,” he said.
“All I’d done this year was have a fifth and a second, it’s been a slow year. But I’ve developed my game a lot although my scores haven’t really reflected it. I feel it’s been a productive year.
“The work I’ve done in the last couple of weeks has been on all aspects of my game.”
Reflecting on the week at Alwoodley, Thornton added: “In my head, after the first day I didn’t see myself not winning this. I was quite confident.”
His initial three holes on Tuesday were a disappointment as he started par-par-double bogey.
“They were straight downwind and the second is reachable with a rescue (club) and the third is a driver-and-a-flick par-5,” he said.
“But from there I made six birdies in really hard conditions – and that’s when I finished triple bogey-bogey on that day as well.
“My 65 (his third round) was just really steady, I had a good start, a better one than the last few days.
“When you’re on your game you can start to change your game plan to attack more flags because you know where the ball is going to go, when you’ve got it going.
“I had a good start and then I played steady and made a few more birdies and – I didn’t really think about it – but at the end I was bogey-free.”
After breaking his drought Thornton will hope to make it back-to-back wins when he plays in the South Beach Amateur in Miami just before Christmas.
Alwoodley, which next year will stage the English amateur stroke play championship, the Brabazon Trophy, welcome visitors and will be offering an autumn green fee rate of £55 in November and December. For more information contact the club on 0113 268 1680 or email [email protected]