Gai Waterhouse directing Preview winner and third placegetter towards Victoria Derby in November.

Being trained at Flemington and having performed well in the Penfolds Derby Preview are both positives in the eyes of Gai Waterhouse as Gold Bullion won the lead-up contest with stablemate Ambassadorial finishing third.

Gai Waterhouse first her won the Group 1 Victoria Derby (2500m) in 1995 with Nothin' Leica Dane and 28 years later she, along with co-trainer Adrian Bott, are in contention with a pair of horses now firmly setting course for the Flemington classic on November 4.

Ambassadorial ($8.50) led for most of the 1800-metres with Gold Bullion ($6.50), ridden by Blake Shinn, staying the distance to win in the last furlong.

"I knew that Gold Bullion would be very tough at the end and all he can do is stay," Waterhouse said.

"Ambassadorial is as honest as the day is long.

"They are trained here and they have shown that they can run 1800, now we'll just have to stretch them like a piece of chewing gum (to reach 2500-metres)."

Gold Bullion delivered Blake Shinn a third winner for the day and he believes that the 2500-metres of the Derby is not out of the question for the gelding by New Zealand sire Savabeel.

He thought the late scratchings at the barrier of three runners played into their hands for the result.

"He's got a fair bit of upside and potential," Shinn said.

"The scratchings changed the dynamic of the race but he was strong when it counted and he's on a Derby path and hopefully he can go on with it.

"When this horse came to Melbourne he was a bit playful and he's still a bit coltish.

"He's got more to offer (but) it is hard to know where the ceiling is."

Gold Bullion won by a long-neck margin over the Trent Busuttin and Natalie Young-trained Sunsets ($19) with Ambassadorial a length away in third.

Gold Bullion is rated an $11 chance in pre-nominations Derby markets with Ambassadorial at $15.