Sam Clipperton has spent the past month stripping weight from his slight frame to honour a pledge he made to Godolphin trainer John O'Shea.

The young jockey committed to riding Sweynesse at 50kg in the Doncaster Mile shortly after the three-year-old finished second in the Randwick Guineas on March 7.

By the middle of this week he was down to 51.3kg and within sight of his target.

It almost seems rude to point out the small fact that Sweynesse is borderline to gain a Doncaster start.

The three-year-old was made first emergency for the $3 million race and will only run if one of the 20 horses above him is scratched.

Clipperton has taken a slightly different view.

"I'm not thinking about that," he said.

"I am preparing myself as if he is there and I'm making sure I'm ready to go. The rest is out of my control.

"I will be there fit and ready on Saturday."

Clipperton admits the past month has been hard.

He has been existing on a restricted diet and additional exercise, all without the help of a personal trainer or dietician.

"It has been the best thing for me," Clipperton said.

"I didn't have a great diet and I've been doing a lot of exercising and clean eating, small portions, no sugar.

On a bright note, Clipperton has picked up the Doncaster Mile mount on Destiny's Kiss if Sweynesse doesn't get a start.

But in recognising Clipperton's commitment, O'Shea has booked him to ride Sweynesse in the Group Three Carbine Club Stakes.