My friend Paul Whitehouse told me the news in my local cafe. At first I thought he was practising a sketch for a re-run of the much-missed Fast Show.

Sadly, he wasn’t. Theresa May’s repeated denials of an intention to call a snap election had gone the way of so many of her inconsistent and often fatuous pronouncements. There was going to be an election after all.

First reports were that she had come to this momentous decision while walking in Snowdonia. But it is pretty obvious that, notwithstanding the denials, the Conservative party machine had been cranking up for some time. Nearly 20 years ago, Gordon Brown and his team were geared up to announce operational independence for the Bank of England if elected, but the chancellor-to-be did not finalise the decision until the weekend before. It was a big moment for Brown, the Bank and the nation. Similarly, this election could well be historic – not in a good sense, as I hope to explain – but the decision to call it appears to have been finalised in the wonderful atmosphere of the Snowdonia national park.

I know the area well and can report that, whatever the impression given by the Brexit vote in south Wales and some of the constituencies on the north coast, there is strong support for our membership of the EU among the people I meet in Penrhyndeudraeth and Dolgellau.

I suspect the locals are shocked that a walk in Snowdonia should be associated with an election whose manifesto, the Daily Mail tells us, will herald “Theresa’s Cast-Iron Brexit Pledge”.

I did not get where I am today forecasting the results of elections, and have never forgotten my failure, along with the economist Roger Bootle, to take advantage of the odds of 6-1 against the Conservatives being offered by bookmakers at Ascot the day before the 1992 election.

All I will venture at this stage is to express the hope that we shall not witness the landslide so many people seem to be predicting. Many factors have been cited to explain May’s decision, not least the opinion polls, the persistent criticism of Brown for not having “sought his own mandate” in 2007, and strong pressure from her colleagues. Also, one suspects, a desire to cock a snook at George Osborne, the godfather of the fixed-term parliament.

If she ploughs on, she could end up by 2020 as the most unpopular prime minister since records began

However, I suspect there is another factor: what a latter-day Thucydides might call “the truest cause”. Not to put too fine a point on it, May has called this election to get it out of the way before enough people wake up to how catastrophic Brexit is going to be.

Now, according to May, “the country is coming together but Westminster is not”. Oh yes? That is not my impression. The country is torn apart, but with the honourable exceptions of the Lib Dems, Kenneth Clarke, the Scot Nats and the Greens, Westminster has caved in, lamely accepting the triggering of article 50.

I read somewhere that May, riding high, is the most powerful prime minister since the war. Really? We shall see. One thing is clear: by caving in to the Daily Mail and their fellow Brexiters, she now owns the consequences of Brexit. If she ploughs on, she could end up by 2020 as the most unpopular prime minister since records began – a feat once achieved by Margaret Thatcher, until she was saved by the Falklands war.

At a time when this country has a surfeit of economic problems – for example, the pressure on the health service and social care, the savage cuts to the budgets of state schools, and the rise in crime associated pretty obviously with cuts to the police force – the last thing we need is Brexit on top of a misconceived austerity programme.

After the election there will presumably be a July budget, accompanied by forecasts from the estimable Office for Budget Responsibility, which will begin to show the economic consequences of the government’s acceptance of a referendum that was conducted beneath a veil of ignorance and deceit.

It is no good people fantasising about a “soft Brexit”. Under the “leadership” of May we are leaving the customs union and the single market – a market the inception of which Thatcher did so much to foster. And the economic consequences?

They are devastating. As Llewellyn Consulting points out, not only is the EU the UK’s largest export market, “the US, the UK’s second-largest trading partner, is significantly less important than the EU”. Of course, the Brexiters go on and on about the opportunities posed by trade with the US and Asia. But, again, “Asia’s big three economies (China, Japan and India) are less important still”.

All the evidence is that the free-trade agreements that the Brexiters promise us will take many years to negotiate. Llewellyn Consulting estimates that leaving the single market and reverting to a free-trade agreement with the EU could reduce our exports by approximately 20%. Given that exports are 20% of our gross domestic product, “the net effect would be to reduce UK GDP by around 4%”.

At a time when Paul Johnson, the director of the Institute for Fiscal Studies, is warning that the pressures on the public finances are enormous, and posing serious implications for the nation’s taxable capacity, the implications of a suicidal abandonment of our main export market are immense.

There is only one sensible option. It is to remain in the market that we are told “the people” want to leave. I fear that May came to quite the wrong conclusion in my beloved Snowdonia. And it is the younger generation that are going to suffer most, unless they revolt.