Global racing power Godolphin has savoured a Group One win in the Doncaster Mile, with It's Somewhat leading all the way in a major upset at Randwick.

Ridden by Hong Kong-based expat Zac Purton, It's Somewhat ($31) went straight to the front and was never headed in Saturday's showpiece.

Last year's runner-up Happy Clapper ($7) gave chase but came up half a length short with Sense Of Occasion ($61) leading the rest of pack 3-1/2 lengths further away.

Trainer John O'Shea's last Group One win for Sheikh Mohammed came with Hartnell in the Turnbull Stakes in the spring.

"It's unbelievable to think we've won it," O'Shea said.

"Daz (Darren Beadman) and I watched it in the jockey's room and we were having an ordinary day, to be fair. When he shot clear I thought, 'Should we cheer yet?' I forgot who was riding it."

Purton said he had had a comfortable run all through the race.

"It's been hard to make up ground today. I went back and looked at the race he won here over 2000 metres and I really liked the way he used his action," he said.

"John said earlier in the day, 'Do you want to be positive?' and I said, 'Yep'. He said, 'Good, he's fit, so use his action'.

"The plan wasn't necessarily to lead but I got there comfortably and I just let him bowl along."

Godolphin Australia managing director Henry Plumptre said the heavy track helped the former English horse, which was placed in the 2014 Coral Eclipse.

"He eats up this ground and he's been flying," Plumptre said.

O'Shea said It's Somewhat was not a flashy type.

"He's just a workman horse," he said.

"We thought he'd finish in the top four or five but just the way the track was playing, we had to ride the track and he's a tough horse and it was a great Zac Purton ride.

"It was a tremendous team effort."

Happy Clapper's trainer Pat Webster admitted the result was hard to swallow after the tough gelding ran second to Winx a year ago.

"The other horse got the soft lead," Webster said.

"It looked like Happy Clapper would go past him and yes, it's hard to take.

"We'll see how he pulls up but we'll get him ready for the 2000 metres and go again next week."

The 2000m is the distance of the Queen Elizabeth in which Happy Clapper finished third to Lucia Valentina last year but will have to take on Winx this time around.

Sense Of Occasion's Kris Lees-trained stablemate Le Romain was the $4.80 favourite but weakened in the run home to finish 15th of the 20 runners.

"I got held up," Le Romain's jockey Hugh Bowman said.

"He's not a sit-and-sprint horse and that is what I needed him to do."