THE VOTE IN NUMBERS

Boris Johnson faces a challenge to win today’s vote, with the DUP confirming they will vote against the Government’s new Brexit deal. A total of 635 votes will be in play when the deal is debated – meaning the Government needs at least 318 votes.

Here are four scenarios.

• Scenario one: If every Conservative MP who is able to vote also backs the deal, this gives the Government 285 votes – 33 votes short of a majority. This shortfall could be met through a combination of votes from Labour and Independent MPs.

• Scenario two: Not every Conservative MP may decide to back the Government. A handful of Tory MPs might follow the example of the DUP and vote against. If 10 of them do so, this would reduce the number of Tories in favour to 275, leaving the Government 43 votes short of a majority. But more Labour MPs than expected could support Boris Johnson’s deal.

• Scenario three: If Jeremy Corbyn manages to keep the number of Labour MPs backing the Government to – at most – a dozen, and a handful of Conservatives vote against the deal, then Boris Johnson could be in trouble. In this scenario, 275 Tories vote in favour, along with 23 Independents but only 12 Labour MPs. This would leave the Government with 310 votes, eight short of a majority.

• Scenario four: MPs might vote in favour of an amendment that requires the Government to ask for an extension if other Brexit-related legislation has not been passed before October 31. This could mean that the deal is approved in principle today but the UK would not leave the EU until the full Withdrawal Agreement – which implements the deal – is also passed.