Wendy and Will Read were well aware their travel documents were due to run out shortly after the trip. Since the couple were planning to travel close to the passport expiry dates, they had checked with the Foreign Office whether their documents would cause a problem.

The official advice remains as it has been since the Czech Republic joined the EU in 2004: “Your passport should be valid for the proposed duration of your stay; you don’t need any additional period of validity on your passport beyond this.”

The couple had provided BA with details of their passports weeks in advance. Any issue could have been picked up then – but of course wasn’t, because they were legally entitled to fly to Prague.

On an airline that handles tens of millions of passengers each year, ground staff will occasionally make mistakes. But if travellers such as Mr and Mrs Read ask to talk to a manager, he or she should be able to assess the two key questions. Is the passport valid? And is the holder travelling to an EU country?

If the answer to both is “Yes”, then they should be allowed on the plane.

British Airways compounded its error by continuing to insist, more than a week later, that it was right and the passengers were wrong. A member of BA’s customer-services team told Mr Read: “As you didn’t have the appropriate passport and you were denied boarding your flight, I’m afraid this means we can’t offer you a refund of your ticket.”

The story about Wendy and Will Read’s lost city break prompted lots of comment, not all of it taking their side. Steve Hearsey tweeted: “Why oh why leave it so late to renew? Some countries expect six months to be left on the passport before travel can be granted.”

But if a traveller’s passport has enough validity for the trip they wish to make, and they have no plans to venture abroad for a year or two, it is perfectly rational not to renew the document. If I want to buy a pint of milk, it is none of the shopkeeper’s business whether I have £1 or £100 in my pocket; all that counts is whether I can pay for it.

Some readers pointed out that airlines are expected to act as immigration authorities and administer a vast number of complex regulations – with severe financial penalties when they get it wrong. Agreed. But there is nothing complicated about a British passport holder heading for a European Union country. Yet.

As the UK’s departure from the EU approaches, though, expect problems to multiply. The triggering of Article 50 will no doubt be misinterpreted by some as our having left the Euro-party. And once Brexit takes effect, expect some Schengen shenanigans. It is possible that the remaining EU countries will insist on three months’ validity remaining for UK passport holders, as well as fingerprinting and photographing every British visitor as they arrive in Calais, Malaga or Amsterdam. Sounds ridiculously onerous? Well, experience in the US, India and elsewhere shows that “security” always trumps tourism.