In-Sight: Voting begins in UK’s crucial Brexit election

British voters are headed to the polls on Thursday in a pivotal snap election that could unblock deadlock over Brexit. The Conservatives are hoping for a big majority so they can get their EU divorce deal through parliament.

But if Boris Johnson’s party get fewer than 320 votes, it opens the door to a coalition opposition government.

Election arithmetic: what are the key numbers to know?

The UK is split into 650 constituencies, which each returns one MP to parliament based on whichever candidate gets the most votes. That means in theory for a majority, a government needs at least 326 votes, but the peculiarities of the system make that figure more like 320. Johnson’s predecessor, Theresa May, called the last election in 2017 in a bid to get a bigger majority to push through Brexit. But her bid backfired and the Conservatives won just 317 seats — 13 less than the previous election — forcing them to form a minority government with the Democratic Unionist Party in Northern Ireland.

What are the key constituencies to look out for?

Scotland, which voted against Brexit, is a fascinating part of the election plot and it has more than a dozen seats where the Scottish National Party (SNP) are defending narrow majorities. A strong performance by the SNP would hit Conservative chances of getting a majority and pile the pressure on for another referendum on independence from London. The Conservatives were nearly wiped out in Scotland after the 2015 election but won 12 seats back last time out.

Incumbent Stephen Kerr holds Stirling with the Conservatives’ narrowest majority in Scotland, with just 148 votes. In England, there are plenty of seats where the incumbent MP appears to grate with how the constituency voted in the Brexit referendum. The constituencies of Jo Swinson and Boris Johnson have also come under the spotlight.

How did we get to this stage?

Former UK PM Theresa May and Johnson both tried to get different versions of a Brexit deal approved by MPs. Both failed. That was down to the Conservatives’ dwindling majority and the stalemate over Brexit made a fresh election — the UK’s third in just four years — inevitable. But while Brexit prompted the election, the campaigns have focussed more on the National Health Service and spending pledges.

What will happen on Thursday?

Polls have opened at 8 am and will close at 11 pm, with exit polls due out shortly afterwards. They are based on interviews carried out with voters outside polling stations, whereas opinion polls ask people who they intend to back in the election.

Official results are then announced by constituencies across the country, with a winner expected to be declared in the early hours of Friday.