The gelding is a graduate of Karaka 2018, bought for $140,000 by trainer Cliff Brown during Book 1.
Inferno began his career with a win in early July, then added the Golden Horseshoe (1200m) less than two weeks later. He resumed his career with a win on October 20, then collected more black-type spoils with Sunday's superb performance.
Rider Michael Rodd had Inferno poised to pounce just behind the leaders, then let him go in the straight and he bounded to victory by a length and three-quarters.
"I've trained a few good horses, like Debt Collector (NZ) (Thorn Park)," Brown said. "To win five Group 1 races, you can't be average to do that.
"This guy (Inferno) is an exciting horse, he's on the right way, but he's still got a long way to go.
"That was really good, we enjoyed that. He wants 1400 metres now.
"Obviously, we were all a little nervous, but we're very pleased he won, and always relieved when it comes off.
"It's always a team effort. We have the good ones and the slow ones, but that's what it's all about, especially for staff who has been with me for a long time.
"Credit must also go to Chris Bock, who is the one who bought Inferno. Chris has been with me a long time, 23 years, he's like my brother.
"I talk to him all the time. A lot of things have to get past him, Chris is pivotal to the buying of horses and the success of the stable."
Inferno has now earned more than S$290,000 in prize-money for owners Barree Stable. That is the equivalent of more than $336,000, which is two and a half times his purchase price.