"It's definitely the best moment of my pro career so far, and the round today is up there among the best of my life," said 27-year-old Stewart after winning his first EuroPro Tour event. "I didn't play golf at all last year, I'd had enough of it. But I decided to give it a go this year and see what happens.
"I think I can finish in the top five now and get on to the Challenge Tour. Another win would make sure of that."
Starting the day four shots off the lead at two under at Wychwood Park Golf Club, Stewart raced through the field with his seven-under par round. He birdied the first three holes then picked up shots at the 7th, 12th, 15th, 17th and 18th, his solitary bogey coming at the 9th.
Stewart, from Grantown on Spey in the Cairngorms, finished nine under overall for the three rounds having opened with a 69 then scored 73 yesterday. He had to wait anxiously in the clubhouse for others to finish, and for a while it looked as if his total would not be enough, as overnight co-leader Alex Belt got to 11 under with four holes to play.
But Englishman Belt suffered double bogies at the 15th and 17th, plus a bogey at the 16th, to finish tied sixth at six under.
Scotland's Paul Doherty and Englishmen Paul Grannell and Adam Stott could all have matched Stewart by finding a birdie in the closing holes, but none of them could manage it and those three finished in a tie for second at eight under.
"I got off to a great start today, I hit it to a foot on the second and three foot on the third," said Stewart. "After the front nine, I felt that if I could get to eight or nine under I would have a chance.
"When Alex Belt got to -11 I thought it was over, but it rained heavily for the last few groups and that helped me. I was watching from the clubhouse and preparing myself for a play-off. Paul Doherty and Paul Grannell both had putts from around 15 foot on the 18th to tie but luckily for me they both missed.
"I've been playing well this season but it's not really come together until today."
Stewart previously languished in 63rd place on the Order of Merit with just £812, but has boosted his earnings by £10,000 and is now into the top ten. The top five players at the end of the season will advance to the Challenge Tour, one step away from playing alongside the golfing elite on the main European Tour.