The challenger bank sector has been such a graveyard in recent years that I don’t hold out much hope that Durham-based Atom Bank will ever quite displace the likes of Lloyds and Barclays. Nevertheless, I wish it well. It is just that its claim to have increased productivity by changing to a four-day week does not fill me with confidence. Not only does the bank intend to make four-day working a permanent fixture, it wants other businesses to copy its example. ‘We firmly believe the four day week is the future of working life,’ says ‘chief people officer’ Anne-Marie Lister. ‘We hope that Atom’s experiences will encourage other businesses to make the shift permanently.’ The bank claims that staff retention rates have improved, days lost to sickness have fallen and customer service ratings also improved.

There is an alternative way of looking at Atom Bank – that rather than being a pioneer of the four day week it is simply putting its staff on part-time working. There have always been people who have worked three or four days a week because it fits in better with their lifestyles. There have always been workers, too, who have combined two or more part-time jobs to make a full week’s work. How many of Atom Bank’s staff, I wonder, really are taking their three regulation days off a week – and how many are working on at least one of those days in order to earn extra cash?

But it is Atom’s assertion that all employers could improve productivity by adopting a four day week that really grates. There are some businesses which are full of ambitious, motivated people which could happily get away without having any contracted hours. If workers are sufficiently keen you can pay them by results, not to surrender a specific number of hours. But that certainly doesn’t apply to a workplace that is full of clock-watchers. If you have workers who are just going through the motions, they aren’t going to work harder just because you have granted them an extra day off. They will just thank you very much – and go through the motions for fewer hours per week.

In any case, there are many jobs where you can’t improve productivity simply by being more motivated. A train-driver, for example, is employed to drive trains to a specific timetable. If you cut his working week he can’t drive the same number of trains in fewer hours just because he is feeling more perky as a result of an extra day off. The only way you can improve productivity in such occupations is to improve working practices – for example by improving rostering so that drivers have to sit around for less time waiting for their next train to drive.

But unions tend not to like that sort of thing – indeed, rail unions have been striking all summer at the suggestion they might be expected to modernise working practices. Being offered a four day week would no doubt delight them, on the other hand. But more productive? Er, no.