He did it the hard way, landing the Grandstand Trophy and £7,260 from last-to-go in the jump-off, but it did not apppear to faze him one bit.
Sweden's Angelie von Essen, who was also chasing her second major victory of the week aboard West Falica (Perion x Heartbreaker), clocked 22.04 seconds to leave Epaillard and Christallo A LM (Casall x Corofino) facing a tall order, but they posted a time of 21.43 to secure a dramatic triumph.
Epaillard said: "My horse jumped very nicely. I tried to make my first round as fast as possible so I could go last in the jump-off, and I felt it all went very well. It has been a good start to the show. Not every day is the same in this sport, but we try to do our best."
Belgium's Francois Jr Mathy was third on Polinska Des Isles (Diamant de Semilly x Valespoir Valabry), with Ireland's Breen brothers - Trevor and Shane - fourth and fifth, respectively.
Earlier in the day, Emma Augier de Moussac won the 1.50 Alan Jones Memorial Trophy riding Wembley (Cassini I x Lucky Lionel).