"No, no I haven't [experienced anything like it before]," Smith said in the wake of his dramatic victory on the Gold Coast. "I guess he was from NSW."

If he was, he was soon on his way back after being booted from Royal Pines in bizarre scenes as Smith and overnight leader Jordan Zunic were locked in an epic battle for the Joe Kirkwood Cup.

The man had been sledging Smith from beyond the ropes for a number of holes, ramping it up as Smith lined up a vital approach on the 72nd hole of the tournament when he led Zunic (19 under) by a stroke.

Smith's caddie, Sam Pinfold, reacted furiously as Smith pulled out of his shot. Pinfold raced over to the ropes and demanded the man back off. Moments later, he was being escorted off the links by a security guard.

"He just said a few nasty things there on the left-hand side, telling me not to choke. I tried to just play it off and just as I was coming into the ball he coughed and sneezed.

"Sammy did the right thing there. I don't know what he was trying to achieve."

Whatever the aim, the 24-year-old Smith rose above to claim his first solo win since turning professional in 2013. Already, he has a victory on the PGA Tour in the US, when he teamed up with Jonas Blixt to win the Zurich Classic in New Orleans in May.

But this was a special moment for a youngster many consider to be a future golden boy of Australian golf. He struggled to hold back tears when talking about the support of his parents Des and Sharon, the latter whom he credits with giving him the kind of unflappable nature essential to the successful touring pro.

"Definitely not dad. My mum is pretty resilient, I guess you'd say. It is just golf. You realise that through life. As a teenager, golf is your life. As you progress through life and things start to become more important, you realise it is just golf and you try your best," Smith said.

"It's huge. I remember going up with dad and mum and watching Adam [Scott] and those type of guys at Coolum. It was really one of my goals all year, I wanted to win one down here. Just being in Queensland makes it a little bit special.

"It won't change me much this time. It did last time [Zurich win]. I got a bit ahead of myself last time, thinking it was the easiest game in the world and I could go out and win every week. Had a bit of a battle through the middle of the year. The key is to keep doing what I'm doing and not expect too much."

Smith teed off at minus 14, three shots adrift of the 25-year-old Zunic, who had flirted with a 59 on Saturday before settling for an equal course-record 64. But there was always the feeling the classy Smith would be a huge threat if he could bridge the gap by the time they headed down the stretch.

He did that by the 10th, rebounding from a tee shot in the water on eight, where he miraculously managed to save par with a monster putt. It was a major moment in the day and Smith knew it by the time he made his way to the ninth tee.

"I tried to stay aggressive all day. With Jordan's lead, I knew I had to stay aggressive no matter how close I came. I knew he was playing well. I didn't quite hit the shot I wanted to hit [on eight], just pulled it a little bit.

"Had a perfect number for my drop and hit the bottom of the pin. It was like: 'Am I not meant to win this thing?' Then I holed, I don't know how long it was, it was a fair way. That kept me rolling and kept the momentum going. That was key."

Smith was fourth in the Australian Open last week and had the previous year lost in a play-off to American star Jordan Spieth. As a rookie pro in 2015, he finished tied for fourth in the US Open at the brutal Chambers Bay, announcing himself in style on one of the sport's grandest stages.

Now he joins a list of PGA champions that includes Scott, Peter Senior and the patriarch of Australian golf, Greg Norman, even if Smith has yet to meet the man who now bestows a medal to Australia's player of the year.

Smith helped calm the nerves for the final round by tuning in to the Kangaroos' compelling 6-0 win over England in the World Cup final, just an hour away at Brisbane's Suncorp Stadium.

"I didn't go to sleep until that was over last night. It was pretty cool. I sent a little message to him [Smith] yesterday, so that was cool to see those guys win and then come out here and get it done. It was a bit inspirational, you might say."

Adam Bland finished third on 17 under, just one short of a spot in the play-off, with world No. 13 Marc Leishman in a tie for fourth with David Bransdon. Defending champion Harold Varner III fired a final-round 66 to climb to outright sixth.