Trainer Chris Waller has taken Group One honours 54 times but Winx has given him a first Cox Plate triumph.

Chris Waller's first Cox Plate win turned out to be easier than he thought - both physically and emotionally.

The physical element was taken care of by brilliant mare Winx who won Australia's premier weight-for-age event on Saturday by a widening 4-3/4 lengths.

And her trainer, who wears his heart on his sleeve, was more contained than he thought he might be with his first victory in a race considered part of the big four of Australian racing.

Perhaps that was because the result was pretty much obvious at the top of the straight as Hugh Bowman released the brakes on the favourite Winx ($4.60) as The Cleaner and Arod dropped back after leading the field.

Winx's inner strength kicked in as Criterion ($6) and Irish horse Highland Reel ($8) chased her home to fill the minor placings.

"I could sense she was travelling well and it was a case of keeping going," Waller said.

"She is just such an athlete. I never thought when she was a young horse this was where she would get to.

"The Myer Classic next week for mares was going to be her race. But when they put the prize money for the Epsom Handicap up to a million dollars we decided to go there and the plan changed.

"And she won the Epsom so well. That gave us the confidence that she could win a race like this.

"She is something special."

Winx was special enough on Saturday to lower Might And Power's track record set in his 1998 Cox Plate win, with the mare running the 2040m in 2min02.98s.

It was also Bowman's first Cox Plate win and one to savour.

"I didn't really have a plan," he said.

"But when The Cleaner ran off I made an instinctive move.

"If it came off she wins, if it doesn't then I've gone too soon.

"But I relied on her and she delivered."

Waller rose to prominence with the support of Bob Ingham after the businessman sold the racing and breeding concern he set up with his late brother Jack to Sheikh Mohammed and bought a couple of dozen young horses to race.

His daughter Debbie Kepitis has been around racing all her life and races several horses under her own banner with Queensland businessman Peter Tighe a partner in Winx.

"There's nothing more exciting than to have a mare do what she just did," Kepitis said.

"It is so exciting. There's hardly any words that would say how excited I feel. This is 20 years after Octagonal won the Cox Plate for Dad and Jack."

Waller had three runners in the Cox Plate with Preferment ($14) ninth and Kermadec ($9) second last of the 14 runners.

There were few hard-luck stories in the race with Michael Walker saying Criterion was crowded by the winner but stewards said Bowman was entitled to take the run on the mare.

The Cox Plate was the fourth Group One win this season for the Waller-Bowman combination, a pairing the trainer said was maturing.

"He rides good and I'm learning to train," Waller said.