Final UK opinion poll shows PM May's Conservatives' lead widening

But she first needs to hold her seat in Hastings and Rye on the south coast which might swing to Labour.

The Conservatives can more realistically hope for the backing of one or both of the unionist parties in Northern Ireland, the DUP and UUP, who are supportive of May's Brexit position.

May was criticized for lacklustre campaigning and deadly attacks that turned the election into a debate about national security.

The opinion polls continue to suggest a Conservative lead, although the scale of the advantage in recent studies has ranged from a single point to a double-digit lead for Theresa May.

May's ruling Conservatives are on 44 per cent, Labour at 34 per cent, the Liberal Democrats at 9 per cent, with far- right UKIP at 5 per cent, the Scottish National Party (SNP) at 4 per cent and the Green Party at 2 per cent.

Then came the suicide bombing at a Manchester concert on May 22, which killed 22 people including seven children, followed by Saturday's knife and van attack in London, which left eight dead.

"They wanted this election to be very much a kind of Brexit vote and I don't think that's in the hearts and minds of Londoners at the minute, (not) almost as much as the security is", said Sheard, 22.

May, who was chosen to lead the Conservative Party after David Cameron resigned last year, had frequently promised not to call for a vote before the next scheduled general election in 2020, claiming that the country needed a period of "stability" in the wake of last year's tumultuous decision to leave the European Union. May would end up with a huge Conservative majority in Parliament, giving the Tories a free hand on steering the country through Brexit.

But things did not go to plan.

May, who went into the election with a reputation for quiet competence, was criticized for a lackluster campaigning style and for a plan to force elderly people to pay more for their care, a proposal her opponents dubbed the "dementia tax".

Twenty-two people were killed by a suicide bomber who blew himself up outside the venue of a concert by USA pop singer Ariana Grande on May 22.

In her final message to voters, May appealed directly to the undecided, urging them to support her in negotiating the best deal for Britain as it leaves the European Union.

"We are seeing the terrorist threat changing, we are seeing it evolve and we need to respond to that", May said. But the attacks forced her to defend the government's record on terrorism, and she's promised to crack down on extremism if she wins. Hope that it doesn't have to be like this; that inequality can be tackled; that austerity can be ended; that you can stand up to the elites and the cynics. "This is the new center ground".

The Conservatives have always been strong on defence and security, and they have sought to exploit Corbyn's anti-nuclear stance and his alleged past support for Irish paramilitaries. Usually you'd expect terror to nudge voters towards the right, where parties are more hawkish and trumpet more muscular security, but May was compromised by the fact that she was Home Secretary for years before becoming PM.

"It's important, but it's only one issue amongst several", said 68-year-old Mike Peacroft.

"The turnout among voters could well determine whether we have a clear Tory or a close Tory win - the group for which that is particularly uncertain is younger voters who are in general much more pro-Labour", said polling expert Professor John Curtice of Strathclyde University.