Odds on Britain leaving the European Union plummeted as Britons headed to the polls on Thursday (23 June), with British bookmakers seemingly certain the UK will vote to remain within the 28-country bloc (EU referendum live blog: follow here).

As of 3pm (BST), chances of Britain leaving the EU were lengthening with all the major booking agencies in Britain. Ladbrokes offered odds of 5/1 (meaning a £1 bet would return £6) on a Brexit compared with 4/1 and 9/2 earlier in the day, while odds on Britain remaining within the union shortened from 1/3 to 1/8.

A Remain vote was also 1/8 with Betfair, bet365, SkyBet and Paddy Power, while it was as short as 1/9 with BetVictor and 1/10 with Marathon Bet. Odds on Brexit, meanwhile, lengthened to 11/2 with Paddy Power, Betfair, BetVictor and Boyle Sports.

Stephanie Anderson, politics trader at Paddy Power said: "After opening the day at 1/3 we've had no choice but to cut Remain into 1/12 this morning after a constant stream of money."

With the polls closing at 10pm, bookmakers are anticipating more bets to be placed before counting begins.

"This market has pretty much blown out all of our expectations in that it's already trading at £55m, £5m of that was taken this morning," Betfair spokeswoman Naomi Totten told IBTimes UK. "So we are anticipating quite a lot more for today,"

Given the bad weather that has hit parts of the country, many have suggested the turnout could be lower than anticipated. Analysts believe the higher the number of voters, the better the chances for the Remain vote.

According to bet365, odds to see over 70% of people eligible casting their vote are at 2/5, while Betfair has odds of 2/1 and 11/4 on a turnout between 70-75% and between 75%-80% respectively.

The final EU referendum telephone opinion poll from Ipsos Mori for The Evening Standard, of more than 1,500 people between 21 and 22 June, put Remain on 52% and Leave on 48% and the bookies also expect a close race.

Odds on the Remain campaign securing between 50% and 55% of votes go from 11/8 with PaddyPower and BetVictor to 13/8 with Betfred and Coral and 6/4 with both Ladbrokes and Betfair. Meanwhile, odds on Brexit winning 47% or more votes are 6/5 with Coral.

One way or the other, the vote will, in all likelihood, have serious implications for the British political landscape. Should the Leave campaign win, David Cameron could come under intense pressure and might be even force to resign.

That would pave to way for a new prime minister into Number 10, with Boris Johnson currently the bookies' favourite. The former Mayor of London is at 2/1 with William Hill and Coral to succeed Cameron, while odds on George Osborne – with Cameron arguably the most high-profile figure in the 'Remain' camp – are currently fluctuating between 5/1 with William Hill and BetVictor and 9/1 with bet365.

Nigel Farage might well be celebrating come Friday morning, but the UKIP leader remains a 100/1 outsider to become the next PM. Still, as Leicester City showed last season, rule dark horses out at your peril.