Glen Boss has already done what no other jockey has done.

He is now set to do what he's never done.

The magic run of success Boss has enjoyed in the past few months reached a new peak at Flemington on Saturday when he landed four winners and opened up a 15-win lead in the Melbourne jockeys' championship.

The man who won an unprecedented three successive Melbourne Cups on Makybe Diva has never won a jockeys' title and he isn't talking about winning this one.

But even before the halfway mark of the season, and even with Peter Moody's firepower to assist his closest rival Luke Nolen, Boss has a lead that will be difficult for anyone to make up.

Boss's quartet of Flemington winners included the feature race, the Listed Chester Manifold Stakes (1400m) on British General, a horse who survived the Black Saturday bushfires, but lost its mother in the flames.

British General, the $2.10 favourite, survived a lesser ordeal on the racetrack on Saturday, but his win nevertheless required courage.

Boss took the horse to the front but at the 200m was joined by the runner up Dash For Viz ($10). He rallied to score by a neck with Under The Eiffel ($8) in third place.

The day that may well have sealed the premiership for Boss began with victory on first starter Ms Funovits ($7) in the Better Beyond Plate (1000m).

Trainer John Sadler said his only concern for the filly had been that she might not be suited to a hectic 1000m race.

"She's probably not bred to be up and about in these races at this time of the year, but she had done so well that she deserved to run," Sadler said.

But Ms Funovits ($7) went straight to the front, fighting back after being headed to beat the favourite Thermal Current ($3.80) by a head with Mount Zero ($4.20) third, a further half-head away.

The double came up with British General's stablemate Tuscan Fire who is on his way to an Adelaide Cup start after winning the Rain Lover Handicap.

Tuscan Fire ($2.05) had control of the race for most of the 2600m and scored a comfortable 1-1/2 length win over Crafty Cruiser ($8) with a short-head to Module ($8.50) in third place.

Zabisco ($8.50) made it a treble for Boss in the Comedy King Handicap (1600m), scoring by a long-head from Sussuro ($7.50) with Boom `N' Zoom ($20), third.

Boss hadn't previously ridden four winners on one day in Melbourne but landed five at Gosford in 1995.