To date, the debate over the deselection of Conservative MPs has focused on whether or not individual associations have, or should have, the right to dispose of MPs who are out of touch with their local membership.

The rights and responsibilities of the grassroots are a subject in which this site takes a close interest, but there is another dimension to deselection which may soon be very important: when it is being done by CCHQ and the Party leadership.

How might this come about? Because if last night’s Commons rebellion is any indication, it is looking increasingly likely that Boris Johnson will need to fight a general election if he wishes to fulfil his promise of taking the UK out of the EU, deal or no deal, by the end of October.

Unlike in 2017, when Theresa May’s bid to hold a single-issue poll was derailed by the electorate, a snap election this autumn really would be all about Brexit, and specifically about trying to break the deadlock in the House of Commons. Which will pose a very awkward question for Johnson: what does he do about Conservative MPs who won’t back him on Brexit?

If they have gone so far as to vote against the Government on a motion of no confidence, then that at least ought to be fairly straightforward: nobody who did that could reasonably expect to be a Conservative candidate at the resulting general election. But as we have previously seen during May’s efforts to get the Withdrawal Agreement through, the Fixed-term Parliaments Act has fouled the previously elegant working of this confidence doctrine.

Because the Government can no longer threaten MPs with dissolution if they vote against the central planks of its agenda – what used to be meant by making votes a ‘matter of confidence’ – the latter can indulge in a have-cake-and-eat-cake position of voting down the Government’s programme whilst (separately) giving it their ‘confidence’. Johnson would need to decide what stance to take on such MPs.

The logic of a ‘Brexit election’ is for the Prime Minister to declare that, as far as the Party is concerned, the Government’s Brexit programme is a confidence issue and that failure to support it will result in deselection. (Nothing in the Party’s constitution suggests MPs so targeted would have much by way of procedural defences against such action.)

But that would be a very big step for any leader to take, and risks forcing a small but not unimportant part of the Tory coalition out of the tent.

Single-issue elections do not allow the leeway for personal manifestos the Tory Party has in recent decades granted its MPs. For all their shortcomings, there were reasons previous prime ministers switched to plebiscites.

Deselection also raises the possibility of CCHQ overruling activists in constituencies where the membership support MPs despite (or indeed, because of) their opposition to the Government’s Brexit strategy. A consistent approach to the rights of the membership requires that South West Hertfordshire’s vote of confidence in David Gauke carry just as much weight as another constituency’s decision to no-confidence a Europhile MP.

Faced with a choice between splitting the Party or risking a hammering in a general election which resolves nothing, it is possible to see why prorogation – which I previously described as a largely theoretical option – might seem less of a nuclear option than some commentators assume. Pulling the Northern Ireland Bill and allowing Ulster to have a pointless election in the autumn might, from the perspective of October, seem a price worth paying in Number Ten.