No yardstick by which we can assess whether Liz Truss knows what she is doing - David Behrens

But which experts were these? In a country where the Chancellor of the Exchequer appears not to know which way up to hold a bank statement, expertise is relative. And in the railway industry especially, it’s a fairly low bar.

There had been until last month a baseline below which national standards did not normally slip. Even when we did not trust their propriety – which was often – we still expected a basic degree of competence from our politicians.

But with the PM and her Chancellor behaving like Jim Carrey and Jeff Daniels in a very British remake of Dumb and Dumber, that benchmark has gone out of the window. There is no yardstick by which we can assess whether Mrs Truss knows what she is doing. We can only guess that she does not, on the very sound basis that nothing she has said so far has sounded remotely like a good idea, even to her.

There is, I suppose, a chance that she and Kwasi Kwarteng have discovered a fundamental truth about the economy that had escaped everyone else – in which case we must consider how long we’re prepared to wait to find out what it is. But in reality neither of them is likely to be in office for long enough to prove anything. I don’t know how long Liz has got but I wouldn’t set the oven timer in the Downing Street kitchen, if I were her.

She is not the first Conservative leader to have entered Number 10 on a wave of scepticism. Margaret Thatcher was deeply unpopular when she cut spending on health, education and housing as soon as she assumed office. But she had a clear electoral mandate and five years to prove herself; Liz Truss has neither. And unlike Mrs Thatcher, she does not govern by conviction; only opportunism. If she has a vision at all, she lacks the artistry and clout to communicate it.

So given all that – and the fact that in her first active week she U-turned faster than a naughty schoolgirl who sees the teacher coming – it is hard to draw any comfort from her apparent enthusiasm for Northern Powerhouse Rail, the on-again, off-again plan to build high-speed lines between Liverpool and Leeds. Boris Johnson scaled it back last year but Mrs Truss promised to build it in full when she visited Leeds in July. As a result, the Department of Transport is drawing up plans which it expects to announce this month.

Does that fill you with confidence? No, nor me. Words mean little when you don’t know what you’re talking about – as the PM herself proved when she claimed that no-one’s power bill would be no more than £2,500 next year.

Her latest promise bodes ill for Northern Powerhouse Rail. I can hear the Transport Department’s shredder cranking up as we speak.

But it is in Doncaster that the emptiness of her rhetoric is most evident. The airport she promised to protect just a month ago is due to close for good in three weeks’ time – despite the fact that it has a new link road from the M18 and would soon have got its own rail station.

On her first week in office, Mrs Truss ordered her Transport Secretary to “begin talks with stakeholders” and assured the local Conservative MP that she would “protect this airport and this infrastructure”. By this Tuesday she had retrenched to a vague promise to “see what can be done”, while the South Yorkshire Mayor reported having had no contact with any minister since the closure was announced.

Had Mrs Truss meant what she has said repeatedly about driving economic growth, this would have been a good place to start. As it is, the closure will be an open sore on her premiership.

Her failure to protect Doncaster Airport also confirms the abandonment of the levelling-up agenda promoted by her predecessor as a sop to the former Red Wall voters who put him in office. Too much attention had been paid to reducing inequalities, said the new PM; the priority now was to promote economic growth nationally.

Before she can do that, though, she needs to survive the coming days of knife sharpening by her Tory colleagues. If she does not, we will have yet another tenant at Number 10, put there by a party membership who thought – for reasons best not asked – that Mrs Truss would make a better Prime Minister than Rishi Sunak. Who will be next in line in the Dumb and Dumber franchise? And how long will it be before we start to regret being so beastly to Boris?