The North Shropshire race will see the Liberal Democrats and Labour attempt to leverage Boris Johnson's rash of recent failures against him. If either proves successful, they could wrestle the constituency from his party for the first time since the 19th century. Many Britons will focus on the results as, despite their primarily local significance, they could signal a coming disaster for the embattled PM.

       Organisations collect exit poll data after people cast a ballot on voting day.

       Staff ask people which way they voted, collect the results and then release them to provide a snap result.

       During general elections, results can take up to a day to process as they come from all over the UK, so exit polls are the only way to provide a conclusive, quick decision.

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       Single constituency elections are different, as people await thousands rather than tens of millions of ballots.

       They do not typically use exit polls, as the results come far quicker, often by midnight or early in the morning of December 17.

       Although North Shropshire is an unusual by-election, it will not split from this precedent.

       But that doesn't mean some pollsters haven't tried to divine the results ahead of time.

       Bookmakers have forged ahead and provided odds for potential winners ahead of December 16.

       And they have come to a single consensus; the Liberal Democrats could win.

       Ladbrokes currently has the party neck and neck with the Conservatives, each with odds of 10/11.

       Labour is behind them in third place with distant odds of 50/1.

       Ladbrokes spokeswoman Jessica O'Reilly of Ladbrokes said that while the top two parties are "neck and neck", the results could lean towards a Lib Dem upset.

       She said: "If Chesham and Amersham is anything to go by it wouldn't be a huge surprise to see another Liberal victory."

       Smarkets Politics has come to the same conclusion, putting the Conservatives on a 50 percent chance to win and the Liberal Democrats on 49 percent.

       One bookmaker currently has the party odds-on to win.

       Betfair has the Liberal Democrats ahead with odds of 4/6, while the Conservatives lag on evens.

       Labour are even further from a win by Betfair's reckoning, with their chances reduced back to 100/1.

       Sam Rosbottom, Betfair Spokesperson, said the Conservatives are reeling from a "tough 10 days".

       He added that "political punters" believe "the pressure on the PM will ratchet up again" and stead the constituency from him.