Huge queues of voters have turned out for Britain’s “most important general election in modern memory”, with lines of people snaking around street corners and enduring long waits.

Voter turnout is expected to play a crucial roll in the election result as Prime Minister Boris Johnston warned in his final plea that the outcome remained on a “knife edge”.

Mr Johnson broke with tradition by voting near Downing Street, rather than his own marginal London electorate, accompanied by his rescue dog Dilyn.

His Conservative Party holds an 11-point lead over Labour, narrowing from 12 points last week, an Ipsos MORI opinion poll for the Evening Standard newspaper showed on election day.

The survey showed support for the Tories at 44 per cent, unchanged from a poll published on December 6.

Labour rose one point to 33 per cent, the poll showed.

However the result remains unpredictable, with one in four voters still saying they could change their mind.

Polling booths are due to close on Friday morning (AEST), with the first exit polls expected to give the first true indication of voters’ decisions.

Longest queues I’ve seen in ten years of voting in this country. Election officials in my district agreed. #amvoting #GE2019

— Delia Lloyd (@realdelia) December 12, 2019

Mr Johnson gambled his premiership by triggering the snap election, focusing his campaign on a pledge to “get Brexit done”.

His Labour rival Jeremy Corbyn has instead tried to highlight his party’s credentials on the health service and other domestic issues and pledged to give voters another say in a second referendum.

“You go down the road of Boris Johnson, a sweetheart deal with Donald Trump, we break off any serious relationship with Europe,” he said.

“Or you go down the Labour way, which is the adult, responsible way, of negotiating a settlement which we will all live by, and I will make sure is carried out in a future relationship with Europe.”

Mr Corbyn was greeted by a small number of supporters as he arrived to cast his vote in Islington – and a protester dressed as Sesame Street character Elmo.

It is deeply heartening to see so many Kent @UniKent students voting today- here they are, standing in the pouring rain in a long queue that spans the length of our library ❤️ #UKElection #YouthQuake #GeneralElection2019 #GE2019 pic.twitter.com/lPshpd4sbK

— Dr Emily Guerry (@EmilyGuerry) December 12, 2019

Polls narrowed in the final week of what has largely been a tame campaign – with few gaffes and many stage-managed visits.

On Monday Mr Johnson came under fire for his alleged lack of empathy when he pocketed a journalist’s phone when asked to view a photograph of a four-year-old boy who was forced to sleep on a hospital floor.

The following day, however, Labour’s campaign was rocked when a member of the shadow cabinet was revealed to have poured scorn on Mr Corbyn’s election chances in a leaked recording.

A terrorist attack on London Bridge – which echoed a similar incident in the middle of the 2017 election – briefly disrupted the campaign, but quickly turned political as the Tories and Labour exchanged blows over how to deal with such threats.

Folks, today is the day. Vote Conservative to get Brexit done 🇬🇧 pic.twitter.com/tlLvHvmex7

— Boris Johnson (@BorisJohnson) December 12, 2019

Liberal Democrats leader Jo Swinson said the polls showed it was still “absolutely possible” to deny the Tories an overall majority through tactical voting.

Mr Johnson opted to vote in central London despite a heavy tactical voting campaign to oust him from his own Uxbridge and South Ruislip seat.

He took the seat with a 5034 majority at the snap election two years ago but pro-European Union campaigners have urged Remainers to unite behind Labour’s Ali Milani in a bid to topple the former London mayor this time around.

When the ex-journalist was elected to the seat in 2015, he was living in Islington, famously giving a statement outside his home when declaring for Leave before the 2016 referendum.

-with AAP