ALL work and no play makes Jack a dull boy, as Jack Torrance (Jack Nicholson’s character in The Shining) endlessly typed out in his effort to write a novel before, as so many writers do, going berserk with an axe and trying to murder his family.

We’ve just had a splendid illustration of how a bid to balance work and leisure can lead to carnage, with the Supreme Court’s ruling on Boris Johnson’s attempt to give MPs more holiday in the run-up to the Brexit vote. But no one will pay attention to that, because all the media coverage will be of John McDonnell’s speech at the Labour Party conference, where he declared his intention to get everyone on a four-day week within a decade.

Or rather, the equivalent, a 32-hour week: 10 and a half hours less than the current UK average for full-time jobs. The EU’s Working Time Directive caps weekly hours at 48 (though the UK has an opt-out from it, which Mr McDonnell would like scrapped) but the EU average is 41.2, just an hour less than the UK.

It’s possible that this policy is just an expansion of the pledge in Labour’s last manifesto to create four new bank holidays, in line with the general approach of offering everyone whatever they’d like and nothing they don’t, without any reference to what it would cost. Jeremy Corbyn and Mr McDonnell were until recently singing the praises of Venezuela, which tried this approach, along with many of Labour’s other policies, so that’s perfectly likely.

Since Venezuela’s official inflation rate increased to 53,798,500 per cent between 2016 and 2019 and more than three million people have fled the country as it fell into chaotic despotism, they’ve mentioned this Latin American triumph of socialism rather less often, but on everything from confiscating private assets to not bothering to cost spending, it still seems to be their model.

It’s a bit odd, though, given that the report the party itself commissioned from Lord Skidelsky, while suggesting that it would be nice if people earned more for working less, concluded that a cap on working hours would not be “realistic or even desirable”. It pointed to France, which tried introducing a 35-hour week but soon found “legislation was rendered broadly ineffective by an accumulation of exceptions and loopholes”.

Mr McDonnell says he’s not planning a cap, however, but to realise his aim through “collective bargaining”, “legally binding sectoral agreements” and “increasing statutory leave entitlements”. So far, so characteristically dirigiste.

I can see why it fits his instincts. What I can’t quite see is what the aim is. Cutting the number of individuals’ working hours by slightly more than 20 per cent might create a lot of extra jobs, I suppose, especially if schools, hospitals, the emergency services and other public bodies are going to keep to their current schedules. But the UK currently has the highest number of people in employment since records began, and historically minuscule levels of unemployment.

We don’t have an employment problem, but a productivity one: we produce about 16 per cent less than the rest of the G7 and 22 per cent less than the USA on the basis of GDP per hour worked. And the French experience suggests the cost of living for almost everything bar housing (already extortionate) would rise sharply, which rather brings into question the priority of cutting hours while not raising wages.

Anyway, where would those public sector workers and the money to pay them come from? Or will public services just be 20 per cent understaffed, or open shorter hours? In the private sector, are factories, warehouses, call centres, shops and restaurants expected to employ more people? Are the self-employed and small businesses to be prevented from working?

The difficulty of answering these questions is one reason for asking why it’s any of the government’s business to dictate how much people work, or to dictate precise terms and conditions – beyond those designed to prevent exploitation or ensure workplace safety – to businesses.

Flexibility for those who want to choose their own hours and balance work and leisure is something the market already provides without government dictat – not least in the form of that great bogey of the Left, the zero-hours contract. And contrary to Mr McDonnell’s rhetoric, both job satisfaction and feeling they have the right work/life balance is higher among zero-hours workers than employees as a whole.

But Mr McDonnell would like to impose costs and government restrictions on private business, to create additional costs and restricted public services for the taxpayer, to prevent individuals from making their own choices, and to let trades unions dictate terms and conditions of employment.

We had something of the sort in the early 1970s, in the days of wage councils, the closed shop, widespread nationalisation, currency crises, state-mandated industrial policy, private sector pay caps and government held to ransom by hugely inflationary wage demands and constant industrial action, which was why we were known as “the sick man of Europe”. We actually had a three-day week in those days, but we didn’t like it much.