Eighteen riders made it through to the jump-off at Friday's big class in Belfast and Irish riders held the lead until almost the end, when Britain's Nick Skelton set an unbeatable time.
Cian and O'Connor and his seven year-old mare 'Echo Beach' held the lead until Skelton's round, and had to make do with second place.
Close behind O'Connor was Shane Breen and 'World Cruise' who had set the time to beat early in the competition, while Billy Twomey and 'Anastasia' took fourth.
Trevor Coyle and Marie Burke also finished in the top ten.
