"I was second this year in France to Solow, but I'm very happy to win in Australia for the Australian owners."
De Watrigant said Gailo Chop was better suited at Flemington which was more like tracks the horse was used to at home.
"Gailo likes to run in front. He's a very strong horse," de Watrigant said.
Gailo Chop became the second northern hemisphere-trained Mackinnon Stakes winner in three runnings after Side Glance scored for English trainer Andrew Balding in 2013. The five-year-old races in the colours of Australian owners OTI Racing and Terry Henderson said it was a big thrill.
"The extra dimension from this horse is where he's come from, which is a very small trainer in the south of France and for him to come and perform like this against the world's best puts some more icing on the cake for us," Henderson said.
A race at the Hong Kong International meeting is next on the radar for Gailo Chop in December.
Gailo Chop's determined win gave Melham his 10th Group One.
"Rising Romance put a neck on him and he dug deep and was strong through the line," Melham said.
"I thought his run in the Cox Plate wasn't too bad, things just didn't go his way."
Godolphin's Contributer ($9) loomed in the straight before finishing another long neck away third while Magic Artist, trained by German Andreas Wohler, was a luckless fourth.