Sajid Javid has made a “shock” resignation from the Treasury. “Shock” in the sense of something highly newsworthy and unexpected.

Now that the Chancellor has walked, the first drafters of history are busy connecting the narrative arc to show how the unforeseen departure was actually inevitable.

It is customary in such analysis to state “X was the catalyst for Y. But actually Z was the underlying reason for the breakdown in relations, a division that X merely brought to a head.”

In today’s example, the variables are as follows. “X” is the Prime Minister’s demand that Javid part with his team of advisers and submit to a new joint 10 and 11 Downing Street economic unit. “Y” is Javid’s deciding that he would rather resign than agree to this slight to him and to those who had worked loyally by his side. And “Z” is …

Well, what, exactly is “Z”?

The obvious answer to this – as supposedly to most other questions about the life force powering the Johnson government – is “Dominic Cummings.” The first act in the drama can be traced back at least six months to last August when Cummings summarily dismissed Sonia Khan, a media adviser to the Chancellor. This happened without the Chancellor’s fore-knowledge because Cummings believed Khan had not severed all contact with Javid’s predecessor, the then Brexit-spoiling Philip Hammond.

Revisiting that incident today, one anonymous quote made at the time now takes on rather greater significance. “The truth is they see Saj as a patsy,” an unnamed former advisor confided to The Times the day after Khan was escorted off the premises. “That’s why he’s in there. Whether it’s staff or it’s spending decisions, they think he won’t kick up a fuss.”

Nobody wants to be remembered as a patsy, even if the job comes with the Treasury attached. Did that accusation of cowardice sting? Having not made the removal of his media adviser a matter of honour six months’ ago, was Javid ready to show that this time he was, after all, prepared to lay down his political life for his friends? Once bitten, twice dauntless.

The truth is they see Saj as a patsy

The recent kite-flying (from Treasury sources) about the possible introduction of a mansion tax and a cut to pension tax relief which irritated Number 10 can now be seen as the second tremor before the earthquake.

And yet the reality is that whilst “Z” can reasonably stand for “Dominic Cummings” (or “Boris Johnson”), in the great historical sweep of things it might as readily stand for “?”

Any examination of previous underlying reasons for a breakdown between Prime Minister and Chancellor quickly identify a big theme niggling and waiting to detonate. Nigel Lawson resigned because of the influence of Margaret Thatcher’s adviser, Alan Walters. But that personal antipathy was caused by a major policy disagreement (Lawson’s determination first to have sterling shadow the deutschmark and then join the Exchange Rate Mechanism) which in turn was related to the great faul-tline in Conservative politics from that time until 2019 – the extent of Britain’s integration into the workings of the European Union.

The breakdown between previous Downing Street neighbours was similarly instigated by disagreements that were clear and out in the open such as Imperial Preference (A.J. Balfour and his Chancellor, Charles Ritchie) or mounting inter-personal weariness (Tony Blair and Gordon Brown).

It is a given that Javid and Johnson were not buddies – none who stand in the same leadership contest as Johnson can expect to be. But nor were they two warring parties constantly generating sparks of friction by enforced proximity.

Sunuk will turn on the money-hose held out for him by the Prime Minister and his chief adviser.

There is now an expectation that the new Patsy of the Exchequer, Rishi Sunak, will be even less Gladstonian in matters of financial prudence than Javid was shaping-up to be; Sunuk will turn on the money-hose held out for him by the Prime Minister and his chief adviser. The markets – who are noticeably untroubled by Javid’s exit – seem to believe so. But between Munificent Mr Javid and Munificent Mr Sunak we are comparing apples with apples.

Perhaps then “Z” simply stands for “casual indifference.” The casualness with which a Prime Minister can dispense with his Chancellor for no great matter of state or policy; the casualness with which the markets receive the news precisely because so little is at stake; and the casualness with which Sajid Javid’s parliamentary colleagues take his departure because the ideas he owned were, if we are honest, not that precious.