The first big moment on election night in the UK, after polls close, happens at 10pm sharp. This is when the exit poll is released and the media commentary floodgates are reopened after a day of media silence, according to broadcasting rules.

Lots of polls are published during an election campaign, but the exit poll is different. While most other polls are snapshots of voting intention at a point in time, the exit poll is essentially what everyone wishes a poll could be – a prediction of the election result.

The exit poll is paid for by a media consortium made up of the BBC, Sky News and ITV. The polling and market research company Ipsos collects the data, which is analysed by the expert exit poll team from a secret bunker in central London.

Opinion polls during an election tend to tell you one, or both, of two things: the projected vote share for each political party, and the projected number of seats each party will get. They make these projections by interviewing a panel of people over the phone, or inviting them to take a survey online, where they ask who they’re planning to vote for. Pollsters aggregate and weight responses to arrive at their overall expectation for how the country would vote.

While most polling companies do an excellent job, the people answering those surveys might........

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