“The reform – enacted by statute in 2011 – was generally interpreted as a typical example of Lib Dem constitutional tinkering and a concession by Cameron to Clegg. In fact, it was a Tory initiative, based on the Conservatives’ assumption that the Conservatives, rather than the LibDems, would be the party that slumped in popularity mid-term. “We have to find a way of stopping Clegg from dumping us,” Osborne told his fellow planners.  The stability of a five-year government was what the markets wanted and the Tories needed.  For that, it was worth trading the traditional right of the Prime Minister to decide the election date.”

(From Matthew D’Ancona’s “In it Together”.)

If the Commons passed a no confidence vote in a government, before the Fixed Terms Parliament Act came into effect, the latter would resign and an election would be called.

That’s what took place in 1979 – on the only occasion since the war in which such a vote has been carried – during the days of James Callaghan’s Labour Government.  He lost by a single vote.  Margaret Thatcher went on to win the election than followed, and then two more.

A key point about the Fixed Terms Act is that it replaces clarity with mystery.  If a no confidence vote in a government is carried, there is no automatic general election under its terms.  Instead, the Commons has 14 days in which to pass a motion of confidence in a new government.  If no such motion is passed in that time, an election then follows.

The Act has no answer to the question: who might try to form such a new government?  The Prime Minister, insistent that he or she can win a vote of confidence within the 14 days?  The Leader of the Opposition, making the same claim?  Someone else?

Its silence was deliberate.  “We left all that to politics,” one source who was involved in drawing up the Act told ConservativeHome.  Another reading of the same words is: “we dumped the Queen in it”.  For she must ask someone to form a government, or at least to try to.

Let us now try to imagine how theory might now work in practice..

Were Boris Johnson to lose a vote of confidence in early September, he might calculate that, if 14 days pass afterwards, no election can take place until after October 31 – whether or not the present Commons can produce an alternative government.  In which case – hey presto! – Brexit will happen.

So he would presumably ask the Queen to give him 14 days to form a new government.  Such a request would not be absurd.  For it might be that some Conservative MPs who voted for a no confidence motion to turn him out might also vote for a confidence motion to put him back in.  Other MPs could do the same, too.

This is because there is a difference between bringing down a government, with no election necessarily following, and not putting in a government, if an election must follow the Commons’ refusal to do so.  To put it more plainly, Tory MPs and others might vote for Johnson second time round, rather than face an election that could return Jeremy Corbyn as Prime Minister.

“Look, Liz – give me a chance to have another go,” Johnson might say – or words to that effect.  “I can win that vote of confidence: I really can.”

And given the silence of the Act on the matter, the Queen might say…well, she would be entitled to say more or less anything she likes.  She might say: “Good on you, Bozza – more power to your arm”.  Or she might say: “That’s not what I’m told, so I’m firing you – and sending for that nice Mr Corbyn”.  Or she might say: “Do you know what?  I’ve been thinking.  I’m told that the Commons will go for government of national unity.  I rather like the look of that Dominic Grieve.  So I’m going to send for him.”

For Grieve, read Hillary Benn.  Or Ken Clarke.  Or Yvette Cooper.  Or Oliver Letwin.  Or Chris Bryant.  OK, it almost certainly wouldn’t be the last, but we wanted to check that you are still with us.  Anyone for Nick Boles?

The still point in this turning world is that a Prime Minister must always be in place  The Queen’s Government must be carried on.  Either Johnson must be allowed to try to form a new government, in the event of this one losing a confidence vote, or someone else must be allowed to have a go.  If the last happens, Johnson will become the first Prime Minister to be sacked by the monarch since William IV dismissed Lord Melbourne in 1834.

So what’s your best guess at what might happen if Johnson loses a no confidence vote, given all the above?

We have no idea.  But the landscape would be less bleak for Johnson in such a circumstance than it might appear.  It is by no means certain that all Labour MPs would back Corbyn in a confidence vote – let alone a majority of the Commons.  Are Grieve and company really bent on installing a Marxist government?

Nor is it obvious that the Commons would vote in favour of a government of national unity headed by some grand panjamdrum.  Most Conservative MPs wouldn’t.  And nor would most Labour MPs, surely: fear of deselection, at the very least, would keep them clinging to Corbyn.

And why would Corbyn stand aside, even for a brief period, so that Sir Hillary Letwin can step forward?  Just imagine Seumas Milne’s reaction to the proposal, plus that of the other three Ms: Karie Murphy, Andrew Murray and Len McCluskey.  Oh, and add a fifth M: Momentum.

So the Fixed Terms Act could turn out, in effect, to allow Johnson a second bite at the cherry – one that would otherwise be denied to him.  The Commons might none the less find a way of extending or revoking Brexit.  But the Prime Minister should be grateful for small mercies.  And for this one he can apparently thank…George Osborne.