Bookmakers are predicting a massive pay-out if Tony McCoy's mount Jurancon II wins the Martell Cognac Grand National and Arsenal beat Manchester United in tomorrow's FA Cup semi-final.
The two major sporting events could help spark the biggest betting day in British history.
"The double whammy of the biggest match in the football calendar and the world's most famous horserace will smash all previous betting records," said Coral spokesman Simon Clare.
Warren Lush, spokesman for Ladbrokes, added: "It's 'gunner' be a disaster if Arsenal fan Tony McCoy rides Jurancon II to victory and his team beat Manchester United.
"The champion jockey and the nation's best football team is a match made in hell for bookmakers.
"We have seen what can happen when the country gets behind the champion jockey. Flat champ Kieren Fallon fuelled the biggest gamble in Derby history when Kris Kin won after being backed in on the day from 14-1 to 6-1 last year. Jurancon II is currently 9-1, but that price could collapse."
The big match kicks off at 1pm, while the Grand National is due to start at 3.45pm.
