Bookmakers were left nursing losses totalling up to £30 million after the top seven teams in the Premier League all won their latest round of matches.
"This is as bad a weekend as there's ever been," said Ladbrokes spokesman Ciaran O'Brien, while William Hill compared the impact to when jockey Frankie Dettori rode seven winners at a race meeting at Ascot in 1996.
Bookmakers rely on slip-ups by the favourites - who have the shortest odds but attract the most bets - to help them make money from gamblers.
Ladbrokes estimated that the cost to bookmakers was more than £20 million, while rival Coral put the total bill at £30 million.
"It was another 'magnificent seven' for football customers over the weekend, with the top seven in the league all hammering the bookmakers with winning results," said William Hill spokeswoman Kate Miller.
Ladbrokes, Britain's second-largest bookmaker, will issue a trading update to investors on Thursday, while larger rival William Hill follows on Friday. Happily for them, the updates will cover the period to the end of 2013 and not include the impact of last weekend.