A £100,000 (€121,000) payout was awaiting one lucky punter after Big Buck's romped to an historic victory in the first race of the Grand National Festival in England yesterday.
The unnamed gambler placed £500,000 (€605,000) at odds of 1/5 on the horse to romp to its record-breaking 17th consecutive win and won a 20pc return.
The wager, made earlier this week, was the biggest single bet received by William Hill in its 78-year history.
The bookmaker's spokeswoman Kate Miller said: "This ranks as one of the biggest bets ever taken on racing.
"With measly interest rates, and a volatile stock market, the punter was obviously banking on Big Buck's."
The nine-year-old horse, trained by Paul Nicholls and ridden by Irish jockey Ruby Walsh, now holds National Hunt Racing's longest unbeaten run.
Big Buck's beat Sir Ken's post-war record of 16 consecutive wins set in the 1950s, having equalling it when he was victorious at the Cheltenham Festival last month.