In the four-horse jump-off in the 1.50m CSI3* class on Thursday, the Irishman stacked the odds by making up 50 per cent of the lineup.
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The Land Rover Blair Castle International Horse Trials are underway in Scotland, and the 4* is being led by the world eventing champion.
Friday will see Grades I and III Individual Test medals decided and mark the start of competition for Canada's four para-equestrians.
Collins had stayed on board at CEP to ensure a smooth transition to the new management group, Angelstone Events.
Vanessa Mannix (CAN) and Catinka 25, who won the $100,000 ATCO Cup last week, finished a very close second.
The fiercest Para-Dressage competition yet is set to begin in Japan, featuring 77 athletes representing 26 countries.
The CSHA will host the Cup classes at RCRA in Newmarket on October 10, and also a Showcase class for four-year-olds.
The long-time FEI official retired following the Tokyo Olympics and plans to travel to non-horsey destinations (to her husband's delight!)
The world number one piloted Bingo Ste Hermelle to grab a spot in the LGCT Super Grand at the GC Playoffs in Prague in November.
Morton wins the $15,000 CSI3* Kubota Canada class at the Summer Fort Classic, while Kassidy Keith takes the second of three U25 events.