Tonight’s vote is a numbers game. That may seem like a statement of the bleedin’ obvious, but it’s not just about the Prime Minister winning a majority of one. Churchill once said a win is a win and one is enough. In normal circumstances that might be true, but we are not in normal circumstances.

Theresa May won 63% of the vote when she was forced to undergo a confidence vote in 2018. Jacob Rees-Mogg, at the time a critical backbencher, said she had lost her authority, and worse. I wonder if he will be singing from the same hymnsheet tonight if Boris Johnson gets less than 63% of Tory MPs.

I predicted last week that enough Tory MPs would have sent in letter by today. It gives me little pleasure to be proved right. But what follows tonight is much less predictable. Comparatively few MPs and ministers have come out in outright support of the Prime Minister today. Some of the cabinet have failed to pledge their loyalty.

This leads me to believe that the result could be rather closer than most pundits are predicting. One ex cabinet minister has said that there’s even a 10% of Boris Johnson losing.

Here’s what the numbers will mean. There are 359 Conservative MPs. Anything about 269 (75%) for the Prime Minister would put the whole leadership question to bed. I think he needs at least two thirds (239) to be reasonably confident that his long term position is safe. Anything under 215 (60% and he’s in the danger zone. The devil in me wonders if it might be 52-48, just like the Brexit referendum. In that case it would be 186-173, which would be a very narrow majority indeed.

If the result really was that narrow, I suspect the Prime Minister’s instinct would be to call a general election. One senior MP told me today that the Cabinet would stop him. He then had second thoughts and said: “Actually, they probably wouldn’t, the supine bunch of c****”."

Voters don’t like voting for divided parties. Nadine Dorries’s tweets attacking Jeremy Hunt today so not give an impression of unity. Whatever happens tonight these sort of spats need to stop if the Conservative Party has any chance of winning an outright majority at the next election.

Andrew Marr and Ben Kentish will be joining me from 7-10pm so do tune in for all the latest news, the result at 9pm and some great analysis. You can also watch the entire show on GlobalPlayer or on the LBC Youtube Channel.