Glen Boss grabbed the riding honours, landed the biggest plunge and made the boldest prediction of the day at Flemington on Tuesday.

Boss rode three winners, saving his highest praise for the last of them, Crookhaven.

"If he doesn't win a Group race within 12 month, I'm not here," Boss said.

Crookhaven led throughout to win the Williamstown Handicap (1400m) - only the second success of his short career.

As impressed as he was, trainer Mark Kavanagh took a more cautious approach than Boss, but also tipped a bright future for Crookhaven.

"We might have a go at something early in the autumn," Kavanagh said.

"It's hard to stop them when you've got them going."

Boss also caused the greatest damage in the betting ring with his win on British General who was backed from $4 to $2.90 before scoring a three-quarter length win in the George Watson Handicap (1400m).

Boss's treble began with Tuscan Fire in the Byron Moore Handicap (2000m), but he will have only limited opportunity to rack up too many more wins on the horse.

Trainer Dan O'Sullivan is likely to spell Tuscan Fire until the winter when he will embark on a jumping career.