If it's carnival time, it must be Gai time.

And so it proved when Gai Waterhouse walked away from Rosehill on Saturday with two Group One trophies including the diamond-encrusted Golden Slipper.

She also claimed the other major sprint on the program when Sweet Idea won the Galaxy.

While the Gai autumn onslaught in Sydney is predictable, the other three Group One races were not as clear cut.

Japan claimed its first big race in Sydney when Real Impact fought off international performer Criterion to win the George Ryder Stakes.

Imported horse Contributer gave Godolphin its second major win under trainer John O'Shea in the Ranvet and New Zealander Volkstok'n'barrell upstaged the three-year-olds in the Rosehill Guineas.

Waterhouse equalled the Golden Slipper training record of her late father TJ Smith when Vancouver gave her No.6.

"It's a dream come true," Waterhouse said.

And the Galaxy win of Sweet Idea was overdue for the mare whose Group One record includes a third in the Slipper two years ago.

"She's an outstanding mare and I'm so thrilled for the connections. It's everything they've wanted," Waterhouse said.

Volkstok'n'barrell's win was something New Zealand trainer Donna Logan wanted, especially in light of his defeat in the NZ Derby just days before the death of her training partner and former husband Dean.

"It's a long way from Ruakaka to Rosehill. You never know whether you are up to it," Logan said.

The gelding was up to it and he will now head to the Australian Derby as the second favourite.

The presence of four Japanese visitors in Sydney was underlined by Tosen Stardom's second to Godolphin's Contributer and the George Ryder triumph of Real Impact.

Noriyuki Hori needed an interpreter to convey his thoughts.

"I'm very happy to repay the great support I've had here," Hori said.

Godolphin rider James McDonald was aboard Contributer and Real Impact while Tommy Berry rode the Slipper winner, Craig Williams won the Guineas and Blake Shinn the Galaxy.