Irishman Trevor Breen denied Hickstead Derby defending champion Phillip Miller a second straight triumph in a thrilling finish.
Breen, riding 14-year-old Adventure De Kannan, who had an eye removed last year, pipped Miller by two hundredths of a second.
"That horse loves adversity," said Breen, 35.
South African Jade Hooke and the British pair of Harriet Nuttall and William Whitaker tied for third.
Miller, riding last year's winner Caritiar Z, was seeking to become only the eighth rider since 1961 to retain the Derby crown.
However, Breen's 85.17 seconds to the holder's 85.19 in the jump-off head-to-head was enough for the win.
Breen had been doubtful about Adventure De Kannan's future after the horse had surgery but it then recovered to win two classes at the South of England Show in June 2013.
"To come through it all and go out and do that today, he is a true warrior of a horse," said Breen.