Star jockey Craig Williams signed off from Melbourne racing for the season in style with four consecutive winners on Anzac Day, highlighted by his VRC St Leger triumph on Hippopus.

The only hiccup to his afternoon came in the stewards room when he was suspended for seven meetings for careless riding in the feature.

The Gai Waterhouse-trained Hippopus was the second leg of his four-timer, which came in the final races at Flemington on Thursday.

The meeting was Williams's last in Melbourne before he takes up a two-month contract in Japan, although he is set to miss the first meeting of that stint due to Thursday's suspension.

Hippopus looked the standout on paper following strong Sydney autumn carnival form.

His victory gave Waterhouse and Williams their first wins in the Listed St Leger (2800m), which was first run 156 years ago and is one of the oldest feature races on the Australian calendar.

Williams labelled the colt a stayer on the rise after he easily accounted for McNulty by three lengths with another five lengths to Bessano third.

Hippopus had finished second to Philippi in the Group Two Tulloch Stakes two starts ago and fifth to one of the new stars of the turf in It's A Dundeel in the Australian Derby.

"I said to Gai, `if you bring him down and he's pulled up well from the Derby he's just too good for these horses in Melbourne'," Williams said.

Hippopus was in the box seat during the run but when Williams gave him a squeeze to start to pick up approaching the home turn he got into an awkward spot behind a wall of horses.

"But once he got through he really showed his class," Williams said.

"He was really impressive and strong late."

Williams opened his Flemington account with a win on Decircles in the Auckland Racing Club Hcp (1200m) and rounded out his day with wins on Brisbane Cup-bound Zevada in the RSL Plate (2000m) and Notice Received in the Kokoda Track Handicap (1610m).

Williams will compete at the final meeting of Sydney's autumn carnival at Randwick on Saturday before leaving for Japan.

Stewards at Flemington initially handed him a 10-meeting suspension for careless riding on Hippopus before Williams made them aware he had been booked for a Group One ride in Japan on May 5.

The stewards reconsidered the matter following that submission and reduced Williams' penalty to seven meetings but he will still miss some important rides in Japan on Saturday week.

He indicated he will consider an appeal.