Tennis Cap made a lot of the early running, before Cooper brought Ted Veale side by side with the leader.
The duo jumped over the last together, but it was Ted Veale who stayed on to earn victory.
The 20-year-old jockey told Channel 4: "I think I am going to have to pinch myself. I can't believe this is happening."
Tennis Cap managed to hold on to second place, while Manyriverstocross finished third.