Britain is preparing to face a hung parliament for just the fifth time in its political history, according to a BBC exit poll, as the ruling right-wing Conservative party is set to fall short of an overall majority in the General Election.

Prime Minister Theresa May and her governing Conservatives had been viewed as strong favorites to win more seats than all the other parties combined in Thursday’s vote. However, May’s party now looks likely to fall short of a parliamentary majority. As it stands, Westminster is braced for political deadlock with major parties expected to urgently prepare plans to enter Downing Street as part of a coalition government.

A hung parliament occurs when no political party has been able to secure an overall majority. In the U.K., a party must secure at least 326 seats from a total of 650 in the House of Commons to form a parliamentary majority. The winning threshold is 323 in reality, as lawmakers from Northern Irish party Sinn Fein do not attend parliament.

Britain has endured hung parliaments four times with the most recent example occurring in 2010; when the Conservatives went on to form an alliance with the center-left Liberal Democrat party. It took five days in May 2010 for that coalition government to be negotiated and formed.

All parties have stressed that they are not keen on forming a coalition. However, assuming the exit poll is accurate, multiple parties joining together to form a parliamentary majority would be the most formal and stable way for the U.K. to be governed.

In the run up to the vote, the left-wing Labour Party and Scottish National Party (SNP) – which seeks to fully devolve Scotland from the U.K. – were rumored to be considering a “progressive alliance“. Despite both parties formally ruling out a coalition deal before the election, SNP’s leader Nicola Sturgeon confessed she would be willing to support a minority Labour government in the event of a political deadlock.

The Conservatives had previously described the prospect of a Labour-SNP alliance as a “coalition of chaos”.

A hung parliament typically makes passing legislation an arduous process for the party in government. This is because, in theory, all other parties in the House of Commons can team up to defeat the government’s proposed laws.

Investors had been especially fearful of a hung parliament ahead of the election as the U.K. is less than two weeks away from beginning formal Brexit negotiations.

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