He has plenty of money. He earns a substantial amount from his investments. And he gets a City firm to prepare his returns rather than doing them himself at close to midnight after a couple of fines from HMRC like the rest of us. In truth, there were not a lot of surprises when the Prime Minister Rishi Sunak published his tax returns on Wednesday. We didn’t learn anything we didn’t already know. And yet, even if they didn’t provide any ammunition for his opponents to attack him with, it was still a mistake to publish them – because it puts us on a dangerously slippery slope.

There weren’t any hidden Russian gold mines, or Cayman Islands trusts linked to arms dealers

It was perhaps always inevitable that Sunak would give in to pressure to publish his tax returns. He is the richest person to occupy 10 Downing Street in many years, and, in an era that puts little value on privacy, he was always going to have to be open about his wealth. As it happened, anyone hoping for a scandal would have been disappointed. There weren’t any hidden Russian gold mines, or Cayman Islands trusts linked to arms dealers. He’s rich, in a slightly boring way, and like most rich people he has lots of investments that generate dividends and capital gains. But we already knew that.

In fact, the real problem with publication is this: it sets a troubling precedent. It is probably no surprise that the Labour leader Sir Keir Starmer will be rushing out his tax returns as well. Very soon, just about every public figure will be required to put their filings with HMRC online for everyone to scrutinise. And not long after that, all tax returns will be published online, as they already are in Norway and several other countries.

True, some people might like that. It will create lots of opportunities for snooping on your neighbours, it will allow you to find out whether any colleagues at the office are earning more than you, and it will allow us all to instantly check the financial status of anyone we know or have dealings with. The dating apps will probably find a way to integrate into profiles. But we will also lose an essential right. Financial privacy.

In reality, there are lots of perfectly legitimate reasons why people might want to keep their financial affairs private. They may not want to share the information with the rest of their family. They might not want neighbours or friends to know how much money they have, or don’t have. It may create difficulties in workplaces, if the occasional star performer is paid more than more pedestrian colleagues. The list goes on and on.

It is perfectly reasonable that each of us should have to tell the tax authorities what we are earning, and answer questions on that if required to do so. But there is no reason anyone should be forced to share that information with the rest of us. Rishi Sunak has taken us a step down that path – and the worst of it is that it will be very difficult to turn back now.