Ciaron Maher and Stern Idol carved a slice of Warrnambool May Racing Carnival history on Tuesday when the hulking gelding prevailed in a Brierly Steeplechase for the ages.

Maher edged one clear of Jim Houlahan as the most successful trainer in the history of the famed carnivals majors – the Brierly, Galleywood Hurdle, Wangoom Handicap, Warrnambool Cup and Grand Annual Steeplechase – when Stern Idol provided him with his fifth Brierly.

The imported son of Raven's Pass did so under 73kg, which is the heaviest weight carried to victory in the metric era and the most since Deckard won under the equivalent of 75.5kg in 1939.

Maher's 15th carnival major win was a huge thrill for the trainer who grew up in Warrnambool before embarking on a training career that now has stables throughout Victoria and NSW.

"Jim Houlahan, he was someone I really looked up to and took a lot from," Maher said.

"I went down and worked for him, he was a phenomenal trainer, phenomenal horseman and a phenomenal person.

"We've got a number of stables and it all comes down to you're only as good as your people. You won't get anyone more passionate than Dec (Maher, assistant trainer) and Willie McCarthy (jockey) and the team and they just love him and they had him spot on today.

"It's pretty special."

Unlike most of his feature wins in Australia, where he has demolished his rivals after opening big mid-race leads, Stern Idol was forced to dig deep to land Tuesday's $175,000 event over 3450 metres.

Defending champion Britannicus was camped just a few lengths off throughout and issued the first challenge soon after straightening, but after seeing him off at the 150m Stern Idol then had to survive a late rally from Instigator, who looked the winner 100m out.

Stern Idol ($1.60) rallied to score by a long-neck from Instigator ($10) with Britannicus ($4.80) three lengths further away third.

"The horse has carried 73 kilos today and they never let me get a breather anywhere," winning jockey Willie McCarthy said.

"He's just an amazing horse. He's the best I've ever ridden and today truly shows that.

Stern Idol is favourite for Thursday's $400,000 Grand Annual Steeplechase (5500m), in which he failed to finish last year when an odds-on favourite, but Maher remains non-committal on a start.

"We'll celebrate today and see how he is tomorrow," Maher said.