Great Britain's Olympic gold medallist Scott Brash moved top of the Global Champions Tour standings with a sixth-place finish in the series' London leg.
Sweden's Rolf-Goran Bengtsson won the day's feature class and its associated £283,000 prize with Great Britain's John Whitaker second.
Brash, 29, one of 12 riders to go clear in both the first and second rounds to book his place in a jump-off.
However, four faults at the last fence allowed Bengtsson to claim victory.
Brash's London 2012 team-mate Ben Maher picked up 16 faults in the first round to end his competition.
"I'm pretty disappointed with myself for having the last fence down," said Brash.
"It's nice to be at the top of the leaderboard but I can't help feeling disappointed."
Brash, who has held the world number one spot for 19 of the last 20 months, is defending the Global Champions Tour title that he won in 2013 and 2014.
The event at Syon Park is the 11th of 15 legs on the Global tour, which visits cities such as Paris, Shanghai, Miami Beach and Doha during the seven-month season.