Astute Missile (trap 4) became the longest-priced winner in the history of the Greyhound Derby when scoring at Towcester at 28/1.
Seamus Cahill's dog had qualified for the final without managing to win any of the five previous stages of the competition, but he chose the best possible time to find his trapping boots and pinged out to leave rivals with smarter early pace standing.
By the third bend, Hiya Butt was in front from trap one, but the winner charged up his inside to lead turning for home.
All the while, the strong-running Tyrur Shay in trap five was closing in from behind and victory looked almost assured for the track-record holder.
But he swung wide coming off the final bend and although he was closing strongly, he still had three-quarters of a length to find at the line.
Kent-based Cahill, who is attached to the track at Hove, has long targeted success in greyhound racing's biggest prize, but cannot have expected it to come with a dog who had come up short at this level so many times before and at the same time looked the type to excel in the future over longer trips.
"I can't believe he finally trapped like we knew he could," said part-owner Geoff Hill. "He's such a strong dog that I knew he had to be in with a big chance as soon as he got out like that. He's a real battler.
"I used to own greyhounds at Walthamstow and I got out of the game when that track closed, but Seamus persuaded me to have a dog with him again and I tell you I'm back now - big time!"
Clares Rocket - sent off favourite at 6/4 - failed to lead and in the circumstances ran a big race to take third, more than five lengths behind the shock winner.
1st - Astute Missile (T4) 28/1
2nd - Tyrur Shay (T5) 7/4
3rd - Clares Rocket (T3) 6/4