Anyone who plies their trade as an opinion journalist, albeit not at the rarefied heights attained by Boris Johnson, can see how he ended up making his lamentable quip about the environmental benefit of mine closures.

It’s counter-intuitive, and in theory poses a tricky question to a left which has clung to the myth of the miners’ cause even as it extolled the urgency of taking tough action on climate change. It might have made the basis for an amusing and perhaps even thought-provoking column.

But a Prime Minister is not a columnist. Nor is there any excuse these days for cracking that sort of joke as if a meeting were private political company. Johnson might have managed to inure the public to outbursts that would sink less able politicians, but his luck will only hold until it doesn’t

If press reports are anything to go by, Tory MPs in ‘red wall’ seats fear that moment may have come. From the Times: “The MP also described the comments as Johnson’s “Ratner moment”, referring to an incident in which Gerald Ratner caused the massive devaluation of his own jewellery company, Ratner Group, by jokingly denigrating its products.”

Likewise, when I appeared on BBC Radio Wales to discuss the comments yesterday, the host said that the phone lines were ringing off the hook. It may feel weird to some outside these communities that the mines still resonate more than thirty years on, but there can at this point be little denying that they do.

There are a couple of problems with the joke. The first is that it leans in to the myths the left tell about pit closures, namely that they were all Margaret Thatcher’s doing. In fact, of the 225 collieries present in Scotland at the point of nationalisation in 1947, a mere 14 were shuttered in the 1980s. (Perhaps he was referring to mines nationwide, but if so – why? He made the joke in Scotland.)

Whilst it would probably have been wisest not to joke about the closures at all, praising Labour for the scale of its pit closures might at least have helped dispel a dogged myth which has long served as a drag on the Conservative Party’s prospects in these communities. But that would have required taking a few minutes to check a few facts, so here we are.

It also cuts right across the new party image Johnson is supposed to be creating. ‘Levelling up’, to the extent it means anything, is supposed to be all about tacking the North/South divide and doing more to help those communities that were left behind by deindustrialisation. What possible purpose is served by making those same people the but of the joke? Who is the intended audience except the old, southern Tory Party of popular imagination?

Whether or not this does become Johnson’s ‘Ratner moment’ probably depends on whether he comes through on ‘levelling up’. If the Government delivers real change to left-behind communities, its new voters may forgive the Prime Minister an ill-judged joke as they have so many before.

If not, however, it may end up costing him the benefit of the doubt, and instead be taken as proof that his heart was never really in it. Just the ‘same old Tories’, again.