The Moonee Valley Racing Club chief executive has summed it up after Winx delivered in the Cox Plate.

"It's the fitting finale to a grand build-up, to see her deliver like that," MVRC chief Michael Browell said.

"To think one horse could win four Cox Plates, she's gone from being a legend to an immortal.

"You'd almost say the best horse this country has ever seen on what we saw today."

A crowd of 38,035 packed into the course to witness history as Winx raced to an unprecedented fourth Cox Plate win, surpassing the feat of Kingston Town's three-straight wins in the early 1980s.

Browell said the build-up started months ago when connections of the champion announced Winx was not going to Royal Ascot and would be aimed towards a fourth Cox Plate.

"The reaction of the crowd was amazing," Browell said.

"The whole carnival has been great and it led up to a grand finale and thank god she delivered.

"We started in March when they committed to a spring carnival campaign.

"To see the preparation go off without fault, the lead-up runs. She presented here in tip-top condition and delivered a knock-out performance."