Conservative Prime Minister Theresa May stunned her country with the announcement on April 18, after less than a year in office.
And with the upcoming negotiations on Britain quitting the European Union left to the winner of the snap poll, the stakes could hardly be higher.
Conservative Prime Minister Theresa May stunned her country with the announcement on April 18, after less than a year in office, that she would seek a new mandate.
The news was even more of a bombshell because May and members of her government had previously repeatedly said that they would respect the electoral calendar, which foresaw the next poll in 2020.
"We have not had a snap election since the 1970s so there is little precedent," said Stephen Barber of London South Bank University.
Labour Prime Minister Harold Wilson, who had led a minority government, sought a parliamentary majority with a snap election in 1974 -- a bid that was ultimately successful.
May will try to wring her own robust majority out of the fresh poll, arguing it would strengthen her hand in the thorny talks with the EU on Brexit.
Although Brexit could be one of the most pivotal moments in British politics for a generation, it has failed to take centre stage during the campaign.
Rather, the issue has generally served as a pretext for personal attacks by May and her Labour challenger about their credibility heading into the exit talks.
"While this is the 'Brexit election', it fell off the radar early on," Barber said.
"In part this is due to the reluctance of May and Corbyn to reopen the debate, instead centring on who is best to negotiate."
Only the centrist Liberal Democrats placed Brexit in the foreground, promising a referendum on the result of the negotiations with Brussels.
But the party got largely squeezed out of the campaign, in which the May-Corbyn head-on clash left little room for its leader Tim Farron.
Twenty-two people were killed by a suicide bomber who blew himself up outside the venue of a concert by US pop singer Ariana Grande on May 22.
Less than two weeks later, on June 3, three men went on a van-and-knives rampage near London Bridge, killing eight people in the heart of the capital before they were shot dead by police.
Both assaults were claimed by the Islamic State group, and marked the first time jihadist violence rocked the run-up to a British election.
Campaigning was suspended twice -- another unprecedented development for a UK election, according to Simon Usherwood of the University of Surrey, who said that the attacks could revive the trauma of IRA bombings of the 1980s.
The bloodshed thrust the issue of security into the heart of the debate, with Corbyn even calling on May to step down over a major reduction in police forces during the six years she was interior minister.
May was at the zenith of her popularity in April when she planned the election, enjoying a roughly 20-point lead ahead of Labour.
Riven by internal divisions, Labour seemed doomed for a record defeat as Corbyn faced repeated challenges to his leadership.
Less than two months later, the situation is unrecognisable.
May stumbled repeatedly on the campaign trail while Corbyn surprisingly found his footing, shrinking the Tories' lead to set up a neck-and-neck race.
May's reversal of fortune has few parallels in the history books, a factor Usherwood put down to her dizzying rise to power to succeed David Cameron in the aftermath of last June's Brexit vote.
"May's unusual because she's prime minister by accident, not popular election, so her popularity has not been tested before in a campaign," he said.
Tim Bale of the Queen Mary University of London called Labour's rise "phenomenal", putting it down to a range of one-off factors.
"It's had a lot to do with the Lib Dems not impacting much, with Theresa May's poor campaign, and Corbyn's ability to mobilise his base and offer something to almost every voter in a Father Christmas manifesto," he said.
"I'd still put my money on a comfortable Tory win -- but who knows?"