The US Presidential Election was the biggest political betting event in William Hill’s history, with the British bookmakers taking in around £4 million in bets.

A female client lost nearly half a million pounds on a single bet on Hillary Clinton to win the election, the bookmaker told Business Insider.

The unnamed woman bet £481,000 (around $AU775,000) on Clinton to defeat Donald Trump, only to lose the money after the surprise outcome. William Hill’s Graham Sharpe told Business Insider over the phone that the woman, who was not British, placed the bet online.

Clinton was the favourite to become the 45th President of the United States but Donald Trump surprised political commentators, financial markets, pollsters, and bookmakers to win the race to the White House.

There were some other huge losses too, according to Sharpe. A customer at one of William Hill’s shops in Northumberland, northeast England, threw away £181,200 betting on the Democrat candidate and a London-based customer put £150,000 on her a day before the election.

The bookmaking industry took a total of around £20 million on US Election bets, with 71% of individual bets placed on Trump to upset the odds and the polls to inflict a shock defeat on Clinton.

John Mappin, a hotel-owner in Cornwall, southeast England, made a profit of £100,000 after placing 30 bets on Trump to win, the first placed when the businessman announced his candidacy for the Republican nomination. The betting shop also paid out £101,750 to a customer in Nottingham who put £37,000 on Trump to make history and win the election.

“Donald Trump started as a 150/1 no-hoper but was very well backed, albeit in smaller amounts than we accepted for long-time favourite Hillary Clinton,” Sharpe said.

He added that the election was a “disaster” for the betting industry, with more customers than ever placing large bets on political markets and winning them. “We’ve paid out lots of money,” he added.

He also pointed out a striking similarity between how British customers bet on Brexit and how they bet on the US Election. “The US Election statistics reflect almost identically the division of stakes and bets for Brexit.

“The odds on the day for the two candidates were almost identical to the Remain/Leave odds on EU Ref day. Brexit became favourite for the first time just before 2am on EU Ref night, Trump at just after 2am on polling night.”

A spokesperson for Ladbrokes told Business Insider this week that if someone put £1 on Leicester winning the Premier League, Brexit, and a Trump victory — all outside bets — they would have made £4.5 million ($AU7.25 million).

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