The departure of Dominic Cummings from Boris Johnson’s administration will, we’re told, provide an opportunity for a “reset”. Certainly there’s likely to be a change of tone, if only because it would be hard to find anyone else who is as determined to have a fight with absolutely everyone. Or at least tell us that, or have their friends tell us that.

But the government’s deepest problem will remain. Indeed, it predated both Johnson and Cummings’ arrival in Downing Street, though they are its parents.

Brexit was marketed by Johnson and Cummings as a policy with no short-term economic harms

It’s a problem exposed whenever we ask the prime minister’s office for an estimate of the economic impact of the government’s proposed Brexit model. Trust me on this: economic modelling matters to governments. Because even if you choose not to add the numbers up, they don’t go away. Margaret Thatcher would have known this. She’d have employed homely, personal-to-national metaphors involving pocketbooks. Alfred Sherman would have found the requisite bit of Dickens – ‘Annual income twenty pounds, annual expenditure twenty-pound ought and six, result misery’. These are traditional Tory themes. Their underlying truths are really still there whenever a minister pops up talking about an “Australia-style” Brexit deal, for example. The problem is not that the government isn’t telling us the truth. It’s that it’s not telling it to itself.

The government can offer estimates of the economic benefit of its trade deal with Japan, for instance, but it has nothing to say about the likely impact of leaving the European single market. This is not because there is no one in the Treasury capable of performing such a calculation, or because there are no economic models for what happens when a country introduces barriers to trade. The only reason that the calculations haven’t been published can be that the government doesn’t want to know the answers.

Whatever the virtues of Brexit as an idea, it was marketed by Johnson and Cummings as a policy with no short-term economic harms. Theresa May never felt able to contradict that idea, and Johnson certainly has no interest in doing so.

Cummings of course set himself up as the enemy of self-deception. He had seen others indulge in it: Tories, Remainers, Brexiteers, sphinxes without riddles, the media, Bismarck’s enemies (I guess), classic third-rate suck-up-kick-down sycophants presiding over shambolic courts. Unlike fey, Oxbridge-educated OEs, such as David Cameron (riddleless sphinx) and Ed Llewellyn (c.t-r.s-u-k-d. sycophant), who didn’t even aspire to shamateurism, Cummings was the illusionless man. He was going to be different; he had read Moneyball. He was going to find out the hard truths about the British government and look them in the eye.

Civil servants, like all functionaries in bureaucracies, know better than to believe such statements. All bosses say they want to be told hard truths, but clearly not all of them do. Nor, whatever they might tell themselves, or have their friends tell others, can all advisors, I mean, bosses, handle being told the truth by their subordinates. Sometimes the truth has to be escorted away from your presence at gunpoint, as Churchill so very nearly put it. Johnson’s government has revealed its preference not to hear some difficult things, so it is reasonable to assume it won’t want to hear other difficult things either.

This is a government that would prefer to hear comfortable things than true things

This, to taste, Nelsonic blind eye, or wilful, frightened disinclination to look your triumphs square in the face, has been sustainable on Brexit because of Britain’s transition limbo. But customs forms are stubborn things. With our final departure from the EU now weeks away, the government finds itself building lorry parks in Kent for queues that ministers can’t quite bring themselves to admit will exist. Businesses are urged to prepare, but the language is of “opportunities” and a “new start”. The ads are confusing because they can’t admit the reality, that moving things in and out of the country is about to get harder and more expensive.

Of course, officials know the truth of their models. In this way, parts of government have come to resemble the Soviet Union: there is a reality that appears in public statements, and a reality around which people are working, and no one can mention that the two aren’t the same.

Once upon a time, being clear-sighted about the world round you was a point of pride for Conservatives. And even for – they tell us, or have their friends tell us – people-who-aren’t-members-of-the-Conservative-Party too. Though these people who aren’t Conservatives do so very often always seem to end up working for the party. But again, we must return to self-deception and its foes. For realistic Tories, “Havel’s Greengrocer” was a core parable, warning against the degradation of a political system that makes you lie and affect to not notice lies, and rubs your face in the fact that that’s just what you’re doing.

Ministers may tell themselves that this refusal to face facts is strictly limited to one area. On other issues, they may say, they want to hear the unvarnished truth. But even if this were true, it’s a message that’s unlikely to have reached officials. The clear signal from the top is that this is a government that would, on the most vital of subjects, prefer to hear comfortable things than true things.

Which leaves us with the great irony of Cummings’ time running Downing Street: a man who was an evangelist for the idea of finding the truth in data oversaw an operation that suppressed data, for fear it might reveal the truth.