The 22-year-old, who only turned professional three months ago, lit up the back nine as he made five birdies on his last seven holes to win by five from playing partner Brady Watt, signing for a five under par closing round of 67.

His maiden Challenger PGA Tour of Australasia victory comes just one week after he finished in a share of third at Webex Players Series Murray River, and the win secures playing rights for the next two years as he also moves up to 18th on the Order of Merit.

“It actually feels so, so cool,” said the New South Welshman. “I was just going through all the players that have even won on the Australasian Tour or played well, and the guys are on this trophy; it means a lot to be able to compare myself to them.

“But I'm actually really excited to get back into another tournament. I'm playing great and really, really happy with how I am mentally and how I am with my game.

“What I took from Cobram was to not change anything. Sunday on the Murray was just not my day and the universe didn't want me to have it, but the universe gave me this one and it's a nice feeling. I didn't change anything today and I just played the best I could.”

Making just his seventh start as a professional, O’Donovan was two strokes ahead before finding the water twice on the fifth hole, eventually carding a double bogey to trail Watt by a stroke.

The winners from Castle Hill. PHOTO: Australian Golf Media.

A birdie for Watt at the seventh saw the gap increase to two before O’Donovan hit back with a gain of his own at the ninth, and then he took advantage of dropped shots by Watt on the 13th and 15th, eventually standing on the 72nd tee with a 4-stroke lead before rolling in his seventh birdie of the day.

“Funnily enough, on the events that I have won, I've actually had something weird happen in the final around every time, and then I've played like a gun on the back,” he added. “On five, I hit the shots that I saw; I didn't play it amazing, but I always find that that little hiccup in the round is a really good wake up call to stay focused and stay present. And it literally kept me powering on for the rest of the round and let me have a mint back nine.

“(This win) gives me a lot of confidence to stick at what I'm doing now and to trust that what I'm doing right now is working.”

World Number 45 Steph Kyriacou was the leading female competitor as she finished third on 18-under in her first outing of the year. The 25-year-old will now head to Thailand for her first LPGA Tour start of her fifth campaign.

Jake McLeod (67) finished fourth on 17-under, two strokes from Dimi Papadatos (70), with Caitlin Peirce (69) one stroke further back. Peirce has moved up to second on the WPGA Tour of Australasia Order of Merit after her fifth start this season.

In the Webex Players Series Sydney Junior event, Zac Oyston won in a play-off against Liam Jordan after the pair finished on 3-over, and in the All Abilities tournament, Kane Leonard won by seven strokes from Steven Alderson on 7-over.