But the former Sydney champion rider is poised to alter his opinion.

Johnston, a larger-than-life figure whose habit of picking up untimely suspensions meant he only partnered Kingston Town to one of his three Plate triumphs, hasn't conceded wonder mare Winx is yet on a par with the star of the early 1980s.

But even he admits that she is very close.

"If she wins her third Cox Plate this year I think she will be right there with the black horse," Johnston told an audience of Moonee Valley patrons at a function to honour Kingston Town's historic feat - and preview Winx's attempt to match it.

"I believe he should be the yardstick on which the term champion is based. I think it's used a bit too loosely in our game," Johnston added.

His fellow jockey and now trainer Ron Quinton - who scored on Kingston Town in one of those Cox Plates victories - was reluctant to go so far, at least just yet.

Sydney-based Quinton, an eight-time Premier rider in NSW, still rates the black gelding as the benchmark, saying that he was "the best horse I have seen in my career in racing. I don't think there's been a better one".

But his view might change if Winx continues on her winning ways through another spring.

She will run in Sydney at the weekend at Randwick over 1600 metres in the group 1 Colgate Optic White Stakes as trainer Chris Waller fine-tunes her preparation for her historic third Plate bid at the Valley in six weeks' time.

Such is the level of interest in her that the TAB felt it newsworthy enough to release a statement on Wednesday pointing out that 99.3 per cent of all monies wagered pre-post for Saturday's contest - including a $17,000 bet - had been for Winx, who was now into $1.08 to make it 20 wins in a row.

Still, she will have some stiff competition when she does line up at Moonee Valley on October 28, with 10 foreign raiders and a host of promising younger horses among the 79 gallopers in first acceptors for the $3.05 million Ladbrokes-backed race.

While Coolmore maestro Aidan O'Brien has not entered his globetrotting star Highland Reel - third to Winx when he was an improving three-year-old in 2015 - the Irishman does have five contenders, including the runner-up in this year's Epsom Derby, Cliffs of Moher.

The five other international entries are a pair from Saeed bin Suroor's Godolphin stable (Prize Money and Best Solution), another Godolphin runner in Charlie Appleby's Folkswood, Willie Mullins' Riven Light and Jane Chapple-Hyam's Kaspersky, a former Italian-trained horse who will be partnered by Michelle Payne.

"We're continuing to liaise with the international stables to see which horses will travel Down Under, while we're also eager to see which of the 18 Australian three-year-olds can emerge over the next month to provide a challenge to Winx," said Racing Victoria's executive general manager of racing, Greg Carpenter.

Valley CEO Michael Browell added: "It is very pleasing to see such a strong list of contenders come through to tackle Winx, including five from the powerful Aidan O'Brien stable, a trainer who knows what it takes to win our legendary race."

O'Brien is the only European trainer to have landed Australia's premier weight-for-age test over the classic middle distance, having saddled Adelaide to score narrowly under Ryan Moore in 2014.

Browell told the crowd at the "Legendary Night" function that a handful of horses had tried to win three Plates but only Kingston Town had succeeded. But Browell felt that had So You Think stayed in training in Australia with Bart Cummings rather than moved to O'Brien's Tipperary yard, he might have joined Kingston Town as a Cox Plate immortal.