Jeremy Corbyn has called Boris Johnson’s bluff. Let’s see if the PM would defy the Commons now

Labour is playing a shrewd game in dragging the civil service and the Queen into this argument

As a weak and divided opposition party trying to gain some traction on the main political story of the moment, and at a time when parliament is on holiday, the usually clueless Labour leadership is employing unexpectedly smart tactics on Brexit. Jeremy Corbyn’s letter to the cabinet secretary, Mark Sedwill, about the constitutional propriety of some of the wilder schemes emanating from Downing Street cannot be simply ignored. A protest from the leader of the opposition to the head of the civil service demands some kind of substantive response. If it doesn’t elicit one, that is itself a story. If it does, then it will take the controversy on a step or two.

The letter follows the shadow chancellor’s threat, half joking, to pack Mr Corbyn into the nearest taxi cab and send him to Buckingham Palace to see the Queen if Boris Johnson attempts to squat in No 10 in defiance of a lost vote of confidence and of the terms of the Fixed-term Parliament Act 2011. The whole spirit and intent of the act is plainly to allow for the Commons to select an alternative government that can command the support of the house if the existing administration, in this case the Johnson government, has lost it. If Mr Corbyn was able to demonstrate beyond doubt he could win a vote of confidence with the support of MPs from across various parties, then he would have a right, under that act, to put his case to the Commons and to win a vote. If he lost the vote then there must be an election.

There is no volume of bluster from Mr Johnson or Dominic Cummings to alter the legal facts. If Mr Johnson wants to break the law and ignore the 2011 act then he would have to face the consequences in court – the threat alone should be enough to concentrate his mind. The latest wheeze to be hatched in the mind of Mr Cummings is for a general election on Friday 1 November, the day after Brexit, on the theme of “politicians vs the people”. This, it is imagined, would be sufficient to summon up the spirit of the 2016 Vote Leave campaign and marginalise Nigel Farage’s Brexit Party, and consolidate the broad right wing of the voting public behind Mr Johnson’s Conservatives, rewarding their delivery of Brexit with a five-year term and a working majority.

It is, at best, fanciful, but it wouldn’t matter in the sense that by then Brexit would be over, and the UK would be a new political country – the Johnson gamble.

The real question is whether Brexit can be stopped, either by means of a vote of no confidence and the operation of the Fixed-term Parliament Act, or by some other stratagem.

The answer to this must be “yes”. As the leader of the Commons, Jacob Rees-Mogg is fond of pointing out parliament only speaks through lawmaking, and the business of the house is conventionally controlled by the government – in effect Mr Rees-Mogg. Yet as Mr Johnson and Mr Cummings so often seem to think, conventions are there to be broken, and the Commons has previously seized control of the parliamentary agenda to thwart a no-deal Brexit not approved of by a parliamentary vote. If enough MPs wish to do so again, then they will find a method to do so, and the likes of Dominic Grieve, Hilary Benn, Yvette Cooper and Oliver Letwin will be setting to work to engineer one. One move might be to cancel the usual recess for the party conferences – perfectly justifiable in the circumstances when MPs have better things to be doing than propping up conference hotel bars. Remember when Donald Tusk told the UK not to waste its six-month Article 50 extension?

In this endeavour the rebels will be supported by a new cadre of experienced and respected ministers sacked by Mr Johnson in his reshuffle, including Philip Hammond and David Gauke. This time round, too, they will find more useful and wholehearted support from the Labour leadership. Whether Mr Johnson lost the vote of confidence or not, and whether he chose to try to defy the Commons or not, then or later a short act could be passed that would stop a no-deal Brexit from happening without prior parliamentary approval. Indeed, that very act would show, just like a vote of confidence, that the government cannot command a majority in the House of Commons, and has no right to pretend that it does.

Labour is playing a shrewd game in dragging the civil service and the Queen into this argument. To be fair, it is Mr Johnson and his “reign of terror” special adviser Mr Cummings who have done so already by threatening to break the law themselves. The courts and the speaker, John Bercow, can also be relied on to enforce the democratic prerogatives of the House of Commons dating back to the Civil War. Mr Corbyn is right to call Mr Johnson’s bluff.