Surgery has worked wonders for the rising four-year-old Cha Siu Bao.

“He was gelded after the Derby and we gave him a three-month spell,” said Lance O’Sullivan, who trains the son of Smart Missile with Andrew Scott.

“He’s back and done a few weeks’ work. He looks great, he’s a completely different horse.”

The winner of two of his 10 starts and fourth in the Gr.1 New Zealand 2000 Guineas, Cha Siu Bao hasn’t raced since the Gr.1 New Zealand Derby when he turned on a rodeo performance out of the gates.