Hong Kong Derby champion Rapper Dragon has died after breaking his pelvis in the Group One Champions Mile at Sha Tin on Sunday.

Champion jockey Joao Moreira pulled up the four-year-old, who was a 1.4 chance in the HK$16 million feature, with 800m to go after suffering the injury. He jumped off immediately with Rapper Dragon taken to the equine hospital at the track for treatment, but he was unable to be saved.

“Rapper Dragon suffered a severe fracture of his pelvis which, unfortunately, was coupled with serious complications. Despite our intensive care in the equine hospital, we were unable to save him,” Jockey Club head of veterinary clinical services Dr Christopher Riggs said.

“We would like to extend out deepest sympathies to all of those involved in the life and care of Rapper Dragon, in particular, owner Albert Hung and his family,” Jockey Club chief executive Winfried Englebrecht-Bresges said.

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Rapper Dragon was chasing his first Group One to cap off an exceptional season, when he became the first horse to sweep the four-year-old series (Classic Mile, Classic Cup, Hong Kong Derby) while he was too strong in the Group Two Chairman’s Trophy last month.

The son of Street Boss started his career in Australia, winning his maiden at Wyong before running second in the Group One Champagne Stakes at Randwick when trained by Gai Waterhouse.

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He was then sold to Hong Kong and had 12 starts for John Moore, winning eight and earning more than HK$30 million in prizemoney.

While the race was marred by Rapper Dragon’s injury, the John Size-trained Contentment proved too strong in the concluding stages under the guidance of Brett Prebble, holding off a late challenge from Beauty Only while Helene Paragon came third.

After the race, Zac Purton, who rode runner-up Beauty Only, fired in an objection against the winner alleging interference in the home straight, but stewards quickly dismissed it, leaving the result to stand.

The win is the second Group One of Contentment’s career, having also won last year’s Queen’s Silver Jubilee Cup, while it is the first major of the season for the leading trainer.

In the other Group One of the meeting, Lucky Bubbles went one better than last year to capture the Chairman’s Sprint Prize.

The Francis Lui Kin-wai-trained speedster ran second to Chautauqua in the HK$14 million feature last year, but took advantage of a top ride from Hugh Bowman to get the result from the favourite Mr Stunning, with Not Listenin’tome in third.