English broadcaster Matt Chapman has described being at Moonee Valley to witness Winx's record-breaking fourth Cox Plate as one of his best moments on a racecourse.

Chapman caused a stir at the barrier draw for the Cox Plate when he questioned whether Winx was entitled to be rated the world's best racehorse.

He ruffled a few feathers, not the least Winx's trainer Chris Waller, who called him a d...head in a radio interview.

"I was lucky enough to be at Morphettville when Black Caviar broke the record and when Makybe Diva won her third Melbourne Cup," Chapman said.

"I saw American Pharoah win the Breeders Cup Classic after winning the Triple Crown and this is certainly up there with the best of them.

"It's very difficult to say what is the best of the best, but as a day it is one I will never forget."

But Chapman said beating Benbatl was not the greatest thing on earth but noted it was not the time to be debating that.

"It's the time to enjoy a great horse that did smash Benbatl up and I wanted to see that," Chapman said.

"At the age of seven when most horses of this calibre retire at age three, four, five if you're lucky, it's an incredible training effort and an incredible effort from the owners to keep her going.

"Everyone who looks after that horse should be very proud."