When voting closes at 2100 GMT, an exit poll will be published simultaneously by BBC, ITV and Sky. It is conducted by pollsters GfK and Ipsos MORI, who will speak to thousands of voters at more than 140 polling stations around the county.

In 2005 and 2010 the exit poll accurately forecast the number of seats won by the largest party. In 2015 it slightly underestimated the number of seats won by the victorious Conservatives, but got the order of the parties right.

HOUGHTON AND SUNDERLAND SOUTH, RESULT EXPECTED 2200 GMT

Due to be the first result of the night. It was one of the first big Leave-voting areas to declare in last year's referendum on European Union membership, shocking markets by backing Brexit more strongly than expected.

It is held by the opposition Labour Party, with a majority of nearly 13,000 votes, but will be closely watched for the fortunes of the anti-EU UK Independence Party (UKIP), which came second here in 2015 with more than 8,000 votes.

UKIP's poll share has collapsed since 2015, and this seat could give an indication of how far May's Conservatives are succeeding in mopping up former UKIP supporters.

NUNEATON, RESULT EXPECTED MIDNIGHT GMT

Considered a national bellwether seat, Nuneaton could provide an early clue of the possible swing between May's Conservatives and Labour. The Conservatives increased their majority here in 2015, despite it being a Labour target, and it provided one of the first indications the Conservatives were on course for victory.

DARLINGTON, RESULT EXPECTED 0030 GMT

This Conservative target seat, which voted in favour of leaving the EU, is held by Labour with a majority of 3,158.

A YouGov regional poll last month showed support for Conservatives had risen significantly in the northeast of England, and the Tees Valley region, in which Darlington sits, unexpectedly elected a Conservative mayor last month.

A win for May's party here could mean she is on track for a landslide nationally, according to polling expert John Curtice.

NORTHAMPTON NORTH, RESULT EXPECTED 0100 GMT

This seat has elected a lawmaker from the winning party at every British national election since it was created in 1974. It is held by the Conservatives with a majority of 3,245.

UKIP, which won more than 6,000 votes here in 2015, are not fielding a candidate so it should be a comfortable win for the Conservatives if they are to increase their national majority.

BURY NORTH, RESULT EXPECTED 0200 GMT

This is a Conservative-held marginal seat, with a majority of just 378 voters. It has been a bellwether seat so if the Conservatives lose it, despite facing no UKIP candidate, it could be a sign they are at risk of losing their majority.

MORAY, RESULT EXPECTED 0200 GMT

The seat of the pro-independence Scottish National Party's leader in Westminster, Angus Robertson, who won it with a majority of just over 9,000 in 2015. At local elections in May the Conservatives won a greater vote share here than the SNP.

If the swing seen then is repeated, Robertson would lose his seat. Moray, which voted in favour of Scotland remaining in the United Kingdom in 2014, was the closest Brexit result in Scotland, with "Remain" just 122 votes ahead of "Leave".

WREXHAM, RESULT EXPECTED 0200 GMT

This seat in Brexit-supporting Wales is held by Labour with a majority of 1,831 and has never been won by the Conservatives.

UKIP, which won more than 5,000 votes here in 2015, is not fielding a candidate this time and Curtice points to it as one to watch for signs that May could substantially increase her majority nationally.

HASTINGS AND RYE, RESULT EXPECTED 0200 GMT

This is the seat of interior minister Amber Rudd, who has played a prominent role in the election campaign and is tipped as a possible successor to Chancellor Philip Hammond. She has held it since 2010, and won a majority of 4,796 in 2015.

The Green Party, which won just under 2,000 votes there in 2015, has agreed not to field a candidate in a bid to help Labour try and unseat Rudd. Pollster YouGov's election model has predicted they could succeed in doing so.

KINGSTON AND SURBITON, RESULT EXPECTED 0200 GMT

This seat is being targeted by the pro-EU Liberal Democrats, who lost it to the Conservatives in 2015.

The area voted strongly to remain in the EU at last year's referendum. Whether the Liberal Democrats are able to overturn the Conservatives' majority of 2,834 will be a key test of how far remain supporters are willing to back May's Brexit plan.

WESTMORLAND AND LONSDALE, RESULT EXPECTED 0300 GMT

The seat of Liberal Democrat leader Tim Farron. He won it with a majority of nearly 9,000 votes in 2015 but his party's expected surge in support due to its anti-Brexit stance has failed to materialise.

Cumbria, where the seat sits, voted in favour of Brexit and the Conservatives are hoping to oust Farron. They are likely to be helped by the fact UKIP, which got just over 3,000 votes there in 2015, are not standing.

BRIGHTON KEMPTOWN, RESULT EXPECTED 0400 GMT

This marginal seat is held by the Conservative minister responsible for financial services, Simon Kirby, with a majority of just 690. It voted strongly in favour of remaining in the EU.

It has been a bellwether at national elections since 1979 and the Green Party, who won more than 3,000 votes here in 2015, are not standing. Labour need to win seats like this if they are to have any chance of being the largest party nationally.

HALIFAX, RESULT EXPECTED 0430 GMT

This is one of Labour's most marginal seats, with a majority of just 428. It voted in favour of Brexit. May's Conservatives launched their election policy document here and need to win seats like this if she is to win a comfortable majority.

It is early days. It's a poll. If the poll is anything like accurate this is completely catastrophic for the Conservatives and for Theresa May. It's difficult to see, if these numbers were right, how they would put together the coalition to remain in office. But equally it's quite difficult looking at those numbers to see how Labour could put together a coalition so it's on a real knife edge, and I think over the next few hours it's going to make a huge difference just a few ... seats because by my reckoning both parties have got coalitions which just fall short of an overall majority. 

If this result is confirmed, Theresa May will have thrown away a bigger majority of 17 seats. There has got to be a good chance that she stands down as Prime Minister in this environment. The betting websites have Boris Johnson as 2:1 to be the next prime minister after Theresa May.