Winx might be the best horse in the country but there is no doubt she is being challenged in the popularity stakes by Happy Clapper, who has won the Doncaster Mile after running second twice.

Saturday's win is Happy Clapper's third at Group One level this season but one that means the world to trainer Pat Webster, who has spent his working life at Randwick.

A young jockey when he came to the track 50 years ago, 67-year-old Webster said the Doncaster was the race he had always wanted to win.

"You can have the Slipper and the Cox Plate. The Doncaster has always been the race I wanted to win," Webster said.

"When we were kids as apprentices, we would sit up on the hill and watch the Doncaster.

"I watched my first Doncaster from the Leger when Tobin Bronze won (1967).

"I grew up here and this is the race I've always wanted to win.

"And I spent a bit of time in the Doncaster Hotel up the road."

And win Happy Clapper did with a perfectly rated ride from Blake Shinn, who got him out quickly from the inside barrier.

The $5 second favourite, Happy Clapper travelled sweetly while $3.20 favourite Kementari started well but was shuffled back as Arbeitsam and Tom Melbourne moved forward.

As the field straightened, Shinn drove Happy Clapper along the fence and the big gelding gave a kick, holding off Comin' Through ($19) by two lengths, with Arbeitsam another half-neck third.

D'Argento ($8.50) ran home well for fourth with substitute jockey Andrew Adkins aboard after Corey Brown had to forfeit the ride when he was injured in the Australian Derby earlier in the afternoon.

Kementari ran 10th after being unable to get a clear run, with his jockey, Brenton Avdulla, blaming himself.

"I stuffed that one up," he said.

For Shinn, who rode Happy Clapper to his previous Group One wins in the Epsom Handicap and the Canterbury Stakes, the Doncaster was also the icing on the cake.

"That is amazing. I have just won a Doncaster," he said.

"I have watched this race for so many years growing up and to finally win it and on the people's champ, 'The Clapper'.

"To win a Doncaster and put my name in the history books with this horse who deserves it is very special.

"He is so brave, this horse. He is honest, he is tenacious and tough."

Happy Clapper's owner-breeder Michael Thomas is another for whom the race is the ultimate.

"As an owner I can hang my hat on a Doncaster," Thomas said.

"It is the race I have always wanted to win."

Webster said all being well, Happy Clapper would front up again next week to take on Winx in the Queen Elizabeth Stakes.

"It's $570,000 for running second. Why wouldn't he go there," he said.