Philip Hammond is usually sensible, but even he can't face the truth about Brexit's damaging economic impact

There are those who see Philip Hammond as the government’s Cassandra – the lonely voice of truth in an administration determined to slowly suffocate the country with a pillow of Brexit related lies.

Except that he’s not. Not quite. He is a shade more honest than most of his colleagues, even though that feat is about as difficult to accomplish as cracking an egg in a glass bowl with a metal spoon.

But in speaking of a £26.6bn Brexit deal war chest and warning that it may disappear in the event of a no-deal Brexit at the annual Mansion House shindig, where the chancellor traditionally serves up his economic state of the nation, he’s still selling a theory that Waterstone’s would have no option other than to put on the fiction shelves next to Hans Christian Andersen and the Brothers Grimm were it to be published.

Grim is likely to be an apt description for the expressions on the faces of the high priests of finance gathered at the official residence of the Lord Mayor of London to listen to him when he gets to that part. They know better than anyone just how mendacious the claim is.

It’s a good thing for Spreadsheet Phil that they’ll all be on their best behaviour so the worst he’ll get in response is maybe be a frown and an occasional roll of the eyes.

The claim of a “deal dividend” was comprehensively debunked shortly after it was made in February by the Treasury Committee, chaired by his Conservative colleague Nicky Morgan.

In a bitingly critical report, it said that it was “not credible" to describe any economic boost from a Brexit deal as such because getting one through as an alternative to no deal would actually amount to little more than “avoiding something really bad”.

Ditto the widely respected and non-partisan Institute for Fiscal Studies, which pointed out that the Office for Budgetary Responsibility’s current gloomy economic forecasts are based on a deal going through, and that even if the chancellor finds a few sweeties to dole out in the short term, they wouldn’t last for long because of the fiscal situation the UK would face.

Hammond is one of those who have been banging the drum for Theresa May’s dismal Brexit, but he has a better understanding of what it will mean for the UK economy than any of his colleagues because he’s overseen the analyses of its impact. Even the government’s more creative spin doctors haven’t been able to turn them into anything more palatable than a turd with a few chocolate sprinkles on top.

Yet still he feels the need to double down on a dividend claim that has no more basis in reality than any of the dribblings from the leadership candidates – those not named Rory Stewart, that is. And they have been serving them up daily in an attempt to woo the few tens of thousands of Tory Party members afforded the privilege of picking our next prime minister for us.

Part of Hammond’s aim in drafting the speech was, of course, to nail the lie that some of them have been touting, namely if we’d only “believe in Britain” then self-imposing the sort of economic sanctions that would be an excellent model for dealing with future rogue states won’t hurt much more than a finger prick.

It’s headmaster Phil delivering a stern warning to the children, and in particular Boris Johnson, the one the sensible teachers all want to avoid when the classroom assignments are handed out.

It is a truly brutal indictment of the state of debate in the Tory Party, not to mention in the country at large, that the only way the chancellor feels he can counter one ugly falsehood is with another, slightly less egregious one.