It started with a horse called Isn't That Lucky and ended with one called A Dream Come True - a run of eight winners that turned a 50p stake into Britain's first million pound betting-shop pay-out.
An unnamed small-time gambler, believed to be in his sixties, backed eight horses to win races in a multiple bet called an accumulator, at combined odds of nearly 2.8 million to one. If just one had lost, he would not have received a penny.
The man is a regular punter at one of William Hill's betting shops in Thirsk, North Yorkshire. He struck his bet on Friday but did not find out about his giant win until he went to place more small bets yesterday.
The punter will collect exactly £1 million in winnings, William Hill's maximum pay-out on horse racing, which it says has never been reached in a betting shop before.
David Hood, a spokesman for William Hill, said: "It is a staggering bet, and earns him a place in history as the world's first betting shop millionaire. Even a scriptwriter couldn't have dreamt this one up."