Stephen Bush of the New Statesman asked a good question the other day. Why do people who hate what Boris Johnson and Liam Fox are doing to Britain go easy on David Davis?

He’s right to be perplexed. It turns out all those trade deals the leave campaign promised can’t be done for years. Liam Fox has nothing to do except be a public nuisance, which now I come to think of it is the only post he’s qualified to fill. Johnson meanwhile is an embarrassment, even to an administration which seems beyond shame, and Theresa May does her best to keep him locked in an FCO cellar.

Davis, on the other hand, is Britain’s chief negotiator, and as such is the most important politician in the country today. Yet he receives little of the abuse directed at his colleagues. The political answer to the apparent conundrum is that Davis won admirers across the political spectrum because of his honourable career fighting for civil liberties, regardless of the cost to his own career in the Conservative party.

That’s true, but it misses the basic point that David Davis is a decent man, while to my mind Johnson, Fox and the rest of the gang are not. If you went to speak to Davis in a bar, he would be interested in you and you would be interested in him. By contrast Johnson wouldn’t speak to you unless you could help his career, while a faint but unmistakeable whiff of sleaziness would drive you from the side of Dr Fox.

There is no contradiction between Davis’s love of civil liberties and opposition to the EU. I’m guessing he doesn’t much care for phrases like 'civil liberties or 'human rights'. When he made a stand against, say, detention without trial he was defending Britain’s traditional liberties – the rights of freeborn Englishmen, as we used to say when women were second-class citizens. It’s not, I’m sure, that he does not want the citizens of other countries to enjoy the same rights as us. It’s just that he sees no need to invoke the United Nations, EU, European Court of Human Rights or any other outside body to protect what Britain (or more specifically England) already owns.

Somehow the notion that civil liberties is an exclusively left-wing cause has survived communism, the PC assault on freedom of speech and successive Labour home secretaries. Davis is a living counter-argument. He is a representative of a tradition that dates back to the opposition to Stuart absolutism, and that stretches through the 'country' opposition to the Whig oligarchy and on to our time. Or rather he was a living counter-argument. For look at him now.

The easy polemical point to make is that he is a willing servant of a government that is preparing to seize power from parliament on a scale that would make a Stuart king nod with approval. Which ever side he would have fought for in the past, he’s on the wrong side at Marston Moor today.

But his failure goes deeper than that. As I keep trying to hammer home, the big lie of the leave campaign was not that Brexit would give £350 million a week to the NHS – although that falsehood ought to have been shocking enough to disqualify all who uttered it from public life – but that Brexit would be easy.

Perhaps it was worse than a lie. Perhaps it was a blunder. For years, to be on the right in British politics meant being anti-EU. If your hatred faltered, you were out of the club. It is extraordinary that in all those years Conservatives never reached a consensus on how we should leave and what we should do next. They loathed the EU, but never understood it or how important it was to British life. They just assumed we could repeal the original common market act and toodle off. Actually, it is worse than extraordinary, it is a shameful dereliction of duty.

Davis is denying now that he ever believed Brexit would be easy. Of course he did. They all did. Or found it politic to pretend that they did so they might fool a gullible public. Britain could ignore Brussels and strike a bilateral trade deal with Berlin immediately after Brexit, Davis told the voters last year. No we couldn’t, as it turned out. We could strike similar bilateral deals with ‘other key EU nations,’ Davis continued. Wrong again. No one need fear the sack, he concluded, because the EU ‘has created next to no jobs for British people in the UK in recent years’. And I think it’s fair to say, he’s going to have that quote thrown in his face for the rest of his life.

The worst moment to date came in August, when he babbled on like a character in a bad sci-fi movie that technology would allow him to create an ‘invisible border’ with the Irish Republic. It would be ‘frictionless and seamless’ and somehow allow the people of the island of Ireland to believe it wasn’t there. This week, he had to admit his idea was barking mad – a 'blue-sky’ plan were his precise words – and recant. I would make a joke of it, if the existence of a hard Irish border had not produced a civil war that only ended in the 1990s.

This is just a taste of the public humiliations to come. If Davis tries to defend Britain’s national interests by compromising, the right that supports him now will turn on him. If he carries on living in the Brexiteers’ world of make-believe, the country will turn on him as our problems grow. Everything Enoch Powell said was either rancid or banal. Top of the list in the banal column is his statement that ‘all political careers end in failure’. Awe-struck journalists still quote it as if it were profound and do not think that, as we all grow old and die, all our careers will end in failure.

In Davis’s case there’s an element of tragedy in the failure. He was a good man, who questioned much, but failed to question his and his supporters anti-European fantasies. He said he was a sceptic, but when scepticism was truly needed, he was not sceptical enough. This will be his tragedy and I fear Britain’s too.