What is the fine-grained topic of the following text: He had stopped running in trials and even races, had a sad story in several more and failed to keep his promises so often that divorce seemed inevitable, yet the faithful forgave it all and welcomed him home as he put away the HK$24 million Audemars Piguet QE II Cup in the twinkling of an eye under William Buick. Only return the topic.
Winning the Audemars Piguet QE II Cup by a formerly unsuccessful racehorse