The vote revealed a new schism between young, educated and professional voters, who backed the Remain camp, and older, less-educated, poorer people concentrated in the former industrial centres of Northern England, who voted Leave. Regional divisions were reinforced too: Scotland and Northern Ireland voted overwhelmingly to Remain, while Wales voted Leave.

The collapse of the UK Independence Party (UKIP) following the referendum, combined with the rout of the Liberal Democrats in the 2015 general election, have left politics in England as a two-horse race between Conservatives and Labour. But the latter has been weakened by the Scottish National Party’s landslide success in 2015, taking all but three of Scotland’s 59 seats at Westminster, 40 of which were previously held by Labour.

The snap election gave the parties little time to put together their campaigns. Despite its crucial relevance to Brexit, the manifestos of both main parties have been predominantly domestic in focus, appealing to disaffected voters in poorer areas, characterised by May as the “just about managing” families or “jams”.

Buoyed by recent local and by-election results, May began by touting her “strong and stable” leadership and taking her battle-bus to traditional Labour heartlands, some of which

were won over by UKIP in the referendum ballot.

The Tory manifesto features increased spending on the National Health Service and schools, greater intervention in industry and a lack of tax cuts, reflecting a return to “one-nation” Conservatism. Meanwhile, the target for balancing the budget has been extended to 2025 – five years later than the party’s pre-referendum goal. On Brexit, it commits to leaving the single market and customs union but allows parliament a vote on the final deal.

Notably, the manifesto proposes reforms to social care for the elderly in England that would raise the savings threshold for free care from £23,250 (HK$233,000) to £100,000, but include property in the means test, with repayment deferred until after death. It stressed that there was to be no cap on the care costs incurred.

Yet four days after its launch, May declared that there would be an “absolute limit” on the costs, attracting accusations of being the first Prime Minister to make a U-turn on a manifesto pledge before the election had even taken place.

Corbyn tore up the New Labour script with a manifesto that pledges to renationalise railways, the Royal Mail, and the electricity and water industries as well as abolish university tuition fees. Spending plans include an extra £4.8 billion for education, £30 billion more for the NHS and £8 billion for social care.

The party plans to fund the increases through tax rises for those earning £80,000 or more and by raising corporation tax from 19 per cent to 26 per cent. On Europe, Labour rejects hard Brexit and May’s “no-deal” option, emphasising retention of access to the single market and customs union.

The polls shifted towards Labour after the manifesto releases, with May’s social care U-turn drawing strong criticism.

TV interviews and debates may have also played a part, with May’s refusal to join ITV and BBC debates going down badly.

Corbyn scored further points after joining the BBC debate at the last minute but blundered on Women’s Hour, where he was unable to cost a flagship childcare policy, while ally Diane Abbott twice got her figures wrong on TV before being taken sick in the final days of the campaign.

A party needs 326 seats to win an absolute majority in the House of Commons, and the Conservatives currently have 330 MPs, while Labour has 229.

But under Britain’s first-past-the-post electoral system the number of seats a party wins is not closely related to their share of the vote. The electoral arithmetic is likely to operate at a granular level, depending on whether swings occur in safe or marginal seats and the interplay of regional factors.

Regional politics has been fuelled by the Brexit vote and even the possibility of Britain breaking up has entered political discourse. The SNP wants to hold a second referendum on Scottish independence once the full Brexit deal is on the table, but May is opposed to the plan.

While the SNP is riding high in the polls, the Conservatives, who currently have just one seat in Scotland, are expecting to pick up some more from voters who oppose Scottish independence.

Less conspicuous but potentially more troubling for unionists is the situation in Northern Ireland. The Stormont government collapsed in early spring following a scandal over a green energy financing scheme and the province is now being administered by civil servants, after parties failed to reach agreement in power-sharing talks by an April deadline. This has now been extended to 29 June, while the parties battle over the province’s 17 seats in Westminster.

If agreement on the regional assembly is not reached by August, Northern Ireland will revert to rule from Westminster. Former Prime Minister Tony Blair, who brokered the Good Friday agreement that brought peace to the province, has warned of the perils that Brexit poses to its stability.

Under the agreement, people in Northern Ireland have a right to both British and Irish citizenship and EU negotiators have indicated that they will welcome the province into a united Ireland within the EU.

Research by the Electoral Reform Society indicates that one fifth of voters are planning to back someone other than their first-choice candidate as part of a tactical voting strategy. Pro- and anti-Brexit crowd-funding campaign groups, such as More United and Open Britain, have been actively promoting tactical voting.

Open Britain has mobilised activists into 29 marginal constituencies where both the majority of the electorate and the incumbent MP voted to remain in Europe, in a bid to increase the MP’s share of the vote. The group, which opposes a “hard, destructive Brexit”, is also campaigning in 21 seats with a strong “Remain” vote where the MP voted “Leave”, to drum up support for a challenger.

Similarly, Gina Miller, the investment banker whose legal challenge in the High Court forced the government to give MPs a vote over its Brexit plans, has launched a Best for Britain campaign that is targeting 36 constituencies - including May’s own seat of Maidenhead - in pursuit of a “soft Brexit” deal.

Other factors that make the result hard to call include the registration of 3 million new voters during the election, many of them young people who are expected to back Labour. But some pundits argue that their impact may be limited because they are predominantly concentrated in safe seats.

Watch: May responds to attacks in London and Manchester

The terror attacks have added further unpredictability, with the parties scrabbling to outdo each other on new security pledges in the final days of the campaign.

The traditional wisdom that security issues tend to favour the incumbent has not played out in recent cases such as the French election.

In last minute campaigning, Corbyn blamed Conservative budgets cuts, which saw the number of police officers fall by ­almost 20,000 between 2010 and 2016, for the attacks in Manchester and London. He slammed May’s suggestion the government could scrap some human rights laws in its crackdown on extremism.

“We won’t defeat terrorists by ripping up our basic rights and our democracy,” Corbyn said.

Meanwhile May tried to put the focus back on the divorce talks with the European Union.

“Give me your backing in the polling station ... to battle for ­Britain in Brussels,” May said in a statement. “Get those negotiations wrong and the consequences will be dire.”

The odds are still on a Conservative victory, with some bookmakers, such as Betfair Exchange, putting them as high as 90 per cent. But the wisdom of Theresa May’s electoral gamble has been questioned by her own supporters, such as the arch-Conservative Spectator magazine.

The pre-election issue lashes the Prime Minister for her lacklustre performance and the damage it has done to her reputation, dubbing her “weak and wobbly” and the election a “general shambles”. Whatever the outcome of tomorrow’s results, with the Brexit talks due to begin 11 days later, one thing is sure: Britain is heading for more “interesting times”.

Additional reporting by Associated Press