Boris Johnson will find out in the early hours of Friday morning whether his big Brexit election gamble has paid off.
Throughout the night, there will be key seats which parties are keeping an eye on to check the health of their overall vote, and some which will be indicators of how the nation will look into 2020.
Sky News has examined some of Britain's most marginal seats and key targets.
Tap on the map below to see if your constituency is a marginal or battleground.
A Conservative holds this seat with a slim majority, but in 2017 there were only three candidates.
This time around there are six candidates vying for votes, so will the 46% of people who voted Remain be split?
In the North West, Bishop Auckland is a Labour seat but the party has a majority of just 502 from 2017. Theresa May hoped the Conservatives would win when she called an election.
Boris Johnson just needs a 0.6% swing to take it.
This seat was gained by Labour in 2017 and they have an 888 majority. It was Conservative between 1987 and 2017 so the party may well be hoping to get it back.
There are only four candidates running this year and Mr Johnson's candidate needs a 0.8% swing to win.
This seat has been marginal since it was created and it was scooped by the Conservatives in 2017, but with just 936 votes in it.
Westmorland and Lonsdale
This seat has been held by the Liberal Democrats since 2005, by former party leader Tim Farron. Despite that lengthy service, his majority in 2017 was 777 votes.
However, he is a Remainer, and the seat voted to stay in the EU, so he might not need to be too nervous.
This is another seat which has been a marginal for a while, but the Conservatives have held it since 2010.
Labour achieved a 9.7% swing in 2017, running the Conservatives down to a 609-vote majority.
Former Conservative MP Jason McCartney is on a mission to regain this seat for his party after they lost it in 2017 to Labour. Labour earned a 915-vote majority two years ago, but Mr McCartney had been the MP since 2010 before that.
Penistone and Stockbridge
Former MP Angela Smith is leaving this constituency to go and fight Altrincham and Sale West for the Lib Dems.
She leaves behind her a very marginal Conservative/Labour constituency where the current Labour MP holds by just 1,300 votes.
Mrs May added this to her short list of victories in 2017, having depleted the Labour majority every year since 1997.
It's a seat which voted 70% Leave and so its Conservative candidate may be helped by the lack of a Brexit Party opponent.
A seat where the current Labour MP has a wafer-thin majority of 30 votes. There were multiple recounts last year, so don't expect to hear this result early.
Former Labour MP Ian Austin was going to stand as an independent, but has told people to vote for the Conservatives, so this could be an interesting seat to watch.
He had a majority of 22 votes in 2017.
Anna Soubry is defending her seat here, having defected from the Tories to form Change UK. She only had an 853 majority before and she is pro-Remain, whereas the seat is pro-Leave.
It will be one to watch to see if a familiar face splits the vote for the Conservative vying to replace her.
This seat has become Labour's 10th most vulnerable and the current MP, Gloria De Piero, is standing down, telling Sky News she'd be spending election night on the sofa with a bottle of chardonnay. The fight to keep the seat will be tough, with a 441-vote majority in 2017.
It's an unusual four-way split here, between Labour, the Conservatives, the Brexit Party and a popular independent called Jason Zadrozny.
This was John Bercow's seat and it hasn't been contested since 2005 because parties don't stand against the Speaker.
Mr Bercow - Sky News' election night guest - had a majority of 25,795 but there wasn't anyone to stand against him. The Lib Dems are hopeful they can beat the Conservatives.
This seat was a huge shock in 2017 when the Conservatives lost by 187 to Rosie Duffield, of Labour. She was one of the most shocked, but is keen to hang on this year.
It's a young constituency, with more than half of adults aged under 45, and it has a student population.
But the Tories need a tiny swing of 0.02% to get it back.
Esher and Walton
A potential flagship seat for the Unite to Remain Alliance, Dominic Raab will be fighting to hold against a single Remain candidate in Monica Harding.
But she has a huge 23,298 votes to overcome.
Hastings and Rye
Amber Rudd is standing down in this seat having left the Conservative Party. She had just a 346-vote majority in the last election.
Labour will treat this as a key marginal.
Not a slim margin in 2017 but an interesting seat this year, as the Conservatives' John Redwood is facing former party colleague Philip Lee, who defected to the Lib Dems and then moved seats.
Mr Redwood has an 18,798 majority but is a Leave supporter. The Lib Dems will be hoping the majority Remain seat will swing to them.
This seat was Labour between 1997 and 2010 before the Tories took it - but in 2017 it became Labour again with a 687 majority. It has a high turnout and is a Remain Alliance target, but for the Green Party candidate, who came third in 2017 and lost their deposit.
A London seat which was previously Conservative and only became marginal when Tony Blair was leader of the Labour Party. But the current Tory has a 353 majority and as a Remain seat it might be slimmed down even further.
Finchley and Golders Green
Luciana Berger has moved to fight this seat for the Lib Dems and the party will be hoping to overturn a Conservative majority of 1,657 votes.
It has a large Jewish population and Ms Berger left Labour over antisemitism, so a test of whether that has paid off.
Another shocker on the same lines as Canterbury, Labour took it from the Conservatives by just 22 votes.
Sam Gyimah is moving from his former seat to fight it for the Lib Dems, but it's usually split between the Conservatives and Labour so he might struggle.
Last year the counting had to be suspended because it went on so long and the counters (and candidates) needed to get some sleep.
Zac Goldsmith's seat until 2016 when he lost it to the Lib Dems in a by-election he triggered over Heathrow - but he got it back in 2017. However, it's a Remain area and he may struggle again this time around, especially with a Remain Alliance against him.
Close to Richmond Park and another seat which has recently swung between the Lib Dems and the Tories, with Vince Cable losing it in 2015 and getting it back in 2017.
He is standing down now so it'll be up to a new name to hold on.
Uxbridge and South Ruislip
The prime minister's constituency, and a small majority for a party leader of 5,034 votes. Labour is hopeful here.
He would be the first sitting PM to lose his seat if he can't hang on.
An inner London seat which was big news in 2017 when a 10-point swing saw Tory minister Jane Ellison lose the seat to Labour. It's strongly Remain and is a very young constituency.
A former Conservative stronghold, Justine Greening sat here from 2005 but was booted out of the Tories and decided to stand down. In 2017 she had a majority of 1,554.
This year there's four candidates and while the Lib Dems are forecast to make good gains in the seat, early predictions show the Conservatives will hang on as Labour won't gain quite enough to close the gap.
A tiny Tory majority of 31 votes here, with exactly the same number of candidates and from the same parties as in 2017. This could be tight, but it's an area which voted mostly to leave the EU, which could boost Mr Johnson's candidate.
The Conservative candidate is fighting to hold onto a few hundred votes which clinched it for her last time.
But with a strong Leave vote of around 70%, she could be helped by both a Green and a Lib Dem standing as well as the absence of the Brexit Party.
Barrow and Furness
This is a seat where the Conservative hopes of gaining might be dashed by the presence of the Brexit Party. The Tory candidate needs just a few hundred additional votes to close the gap with Labour, but might see them go to another candidate instead.
Brecon and Radnorshire
The original Remain Alliance seat, there was a coalition of Remain parties here in 2019 to win the by-election. The same will be happening again.
Sky News will mark this as a Conservative majority of 8,000 because that's how it voted in 2017, but the pact parties will be throwing everything at this to hold.
Vale of Glamorgan
This seat has been marginal between the Tories and Labour, last held by Alun Cairns who resigned as Welsh secretary in November over allegations he knew about the role a former aide played in sabotaging a rape trial and still endorsed him as a Welsh Assembly candidate.
His majority was cut by more than 4,500 votes in 2017, and it's a Remain Alliance seat. However, the candidate chosen is a Green Party candidate and they have not polled more than 2% in since the 1980s.
This seat in North Wales is Labour held and a target for the Tories who want to overturn a majority of 1,832. As one of the earliest seats to declare most years, it's likely it could set something of a tone for the rest of the evening.
One of three seats in Swansea, it's the only one to have turned Conservative in recent years, when Byron Davies won in 2015. He lost it two years later but it's often a target seat for the Tories and with South Wales voting Brexit, it may be more so this year.
Currently held by Conservative Stephen Crabb, he is fighting to hold onto a 300 majority. Labour are coming up close behind him and there are only two other candidates.
A seat for Plaid Cymru to cling to, with 104 votes in it during the 2017 election. There's strong competition from the Lib Dems, and no Remain pact here.
There's 92 votes in it here in this North Welsh seat, where the Plaid candidate will be watching for Labour behind him. But there's no Lib Dem or Green to face, to help ease the pressure of the Remain vote.
It was here that the Conservatives unseated Alex Salmond in 2017, but the SNP only needs a 2.4% swing this time to take it back.
There was a big change in both the Conservative and the Lib Dem vote in the last election, which could have been tactical in order to remove Mr Salmond.
Jo Swinson's seat, which she regained from the SNP in 2017. It's an SNP target, but it's not expected to change hands.
Here the SNP holds with just a 75-vote majority. Labour were close behind in 2017 and this time need a swing of 0.1% to win.
Fife North East
Another slim margin of victory for the SNP here in 2017, winning by two votes. It's the narrowest margin in the UK and equalled the smallest majority ever after the count last time,.
Last time there were three recounts and this time it's another Lib Dem target.
The DUP has a large majority here, of about 8,800, but Sinn Fein, the SDLP and the Greens all withdrew their candidates which gives the Remain Alliance candidate a better chance of getting the 9.9% swing she needs.
The DUP's Emma Little-Pengelly has a majority of less than 2,000 here and isn't facing Sinn Fein, who withdrew a candidate to help the SDLP.
Sinn Fein took 16% of the vote in 2017.
Nigel Dodds, deputy leader of the DUP, might be in trouble here because he faces just two challengers to the seat and defends a 2,081 majority.
The SDLP and the Greens withdrew their candidates, which might help Sinn Fein.
And some of Britain's safest
They may not take their seat for granted, but here are some of the seats with the biggest majorities in the country.
The safest seat in the country, it's held by the Labour Party, and at the last election was won by Dan Carden. He got more than 85% of the vote.
Islington North and Islington South
The former is Jeremy Corbyn's seat and the latter is Emily Thornberry's. Both of them have huge majorities of more than 60% and have been in Labour hands for decades.
The seat held by Labour's Afzal Khan also makes the top 10 least marginal. At 2017 he had a 31,730 majority.
The Brexit Election on Sky News - the fastest results and in-depth analysis on mobile, TV and radio.
- Watch John Bercow with Dermot Murnaghan live from 9pm on Thursday
- Follow the Election Social show hosted by Lewis Goodall and BuzzFeed UK's Emily Ashton on Sky News' website, app and social media channels also from 9.45pm
- See the exit poll live at 10pm
- Watch [email protected] election special on Friday morning