Theresa May (left) and Jeremy Corbyn (right). Photos / File
• Polls open at 6pm NZT
• They close at 9am tomorrow
• Exit polls are expected from 9am with results announced throughout the day
by Nicola Lamb, analysis
Could security, usually seen as a vote-tick issue for conservatives, be a late ballot-shaker for Britain's Labour Party?
At first blink, the advantage appears to be on Prime Minister Theresa May's side as Britain prepares to go to the polls tonight.
She's the incumbent leader, the Conservatives have traditionally been the law-and-order party, and - with six years in the job - she was the longest-serving Home Secretary of the modern era.
Since May became Prime Minister last July, conservative media in Britain have raised her on a plinth cast as the second Iron Lady. Her election campaign, to the much-uttered tune of "strong and stable", has pushed her front and centre.
Her country has just suffered its third terror attack in as many months and May hit bullish, populist straps this week in response.
She declared that "enough is enough" and pressed internet companies such as Facebook and Google to do more to target extremist content online. May said she would change human rights laws if they "get in the way" of dealing with suspected terrorists. The BBC reports that May said she would make it easier to deport foreign terror suspects and "restrict the freedom and movements" of those considered a threat.
Conventional wisdom would suggest that raising the rhetorical drawbridge in a crisis would shore up Tory defences and voters would seek shelter under a "strong" leader within. But maybe not. This election campaign has defied convention and May's castle has taken hits in the past few days.
When May decided in mid-April to call an election in June, it seemed like a good idea at the time. Labour's Jeremy Corbyn was considered the weak head of an unhappily fractured opposition. Why not leap at the chance to consolidate power after the Brexit upheaval?
The Conservatives were ahead by 15-20 points over Labour in the opinion polls. Ipsos Mori's April phone poll even had the Tories on 49 per cent and Labour on 26 per cent. Now, in June, the Ipsos Mori gap is only five (45-40 per cent).
The polls have tightened overall but it is hard to gauge how close the gap is.
Yesterday, for instance, Opinium had the Conservatives leading Labour by seven (43-36 per cent) while on Tuesday Survation had the Tories ahead by one (41-40 per cent) and ICM had the gap at 11 (45-34 per cent).
Those predicted outcomes range from a Conservative landslide to a hung Parliament.
The other main trend has been a consolidation around the two main parties at the expense of the minnows.
The polling average at Twitter site @britainelects has the Conservatives on 44 per cent, Labour 36 per cent, the Liberal Democrats 8.1 per cent, Ukip on 4.3 per cent and the Greens on 2.1 per cent.
There are known unknowns here. How reliable are the polls generally? Which pollsters are more reliable than others? Will the youth vote turn out in sufficient numbers for Corbyn? Will older voters push the Conservatives across the line? Where will the fleeing minor party vote go? Just how much political instability is still floating around after Brexit?
According to commentators, Corbyn has done a reasonable job in the campaign and come across as his authentic self, whereas May has been overly cautious, sticking to grain-fed talking points. In an interview with a local reporter at the Plymouth Herald a week ago, May used the words "I'm very clear" three times, as in "I'm very clear that this is a crucial election for this country".
May's decision not to debate Corbyn didn't sit well with the projection of her as a decisive captain. The party platforms have had an influence. The Independent reports that Labour's plans on tuition fees and childcare were well received but the Tory plan "to force pensioners to pay for care visits in their own home out of the value of their property went down badly".
It is hard not to sympathise with May to some extent with the post-Brexit hand she's been dealt in foreign affairs. Yet the hand-holding with US President Donald Trump at the White House was a disaster in bad optics that she should have wriggled away from.
It was made worse with the invitation for a state visit - another trap of bad judgment May fell into. Now she has been caught in the crossfire of the unpopular President's feud with London Mayor Sadiq Khan.
The aftermath of this week's attack in London has created the most intrigue in terms of impact on the election, with Corbyn hammering May on police cuts of 20,000 while she was Home Secretary.
He called on May to quit and added: "We do have a problem, we should never have cut the police numbers".
Added to that has been a daily drip of revelations about how the attackers were handled. Two of them had been on the radar of police or MI5. One appeared on a television documentary called The Jihadis Next Door.
May told Sky News: "I absolutely recognise people's concerns."
There are clearly ongoing safety issues. Police and intelligence officer numbers are stretched. The agencies say they have disrupted 18 plots since 2013, including five in the past nine weeks, the Washington Post reports.
These issues can't be palmed off as a leftist niche. They cut through to moderate, centrist concerns.
It is a reminder of how old assumptions have been broken in the earthquake and tsunami of Brexit and Trump's election. In this spinning weathervane world, where anti-Trump liberals find themselves on the same page as FBI and CIA agents and Republicans shrug at the idea of a secret back-channel line to the Kremlin, an old-school British Labour leader talking of the need for more cops on the street shouldn't surprise.
Most likely, barring a tornado in the youth vote, the Conservatives will be returned to power. But the election has got tight, and interesting.
Putin signed a decree that enables nuclear weapon use against non-nuclear states.