And to the BBC:

https://www.bbc.com/news/uk-44546400

My apologies if already posted, but I haven’t been following the story in great detail. Although I think this business of deciding what is and what is not an error fare is a very dodgy area. That means, if you simply pick up a special offer, they can simply turn around and cancel it if they feel like it. I flew to Abu Dhabi for €72 with Alitalia (round trip) and at no stage of the trip was it questioned or considered an error fare but it was seen as a special offer that I was lucky enough to have been able to get.

Similarly when I flew GVA-CPH-GVA on LX for CHF69 round trip in Business, it was an offer that lasted for one hour, clearly indicated on their site (similar for my trip a couple months ago from Zurich to Sion and back for CHF58 in Economy, cheaper than the SBB train, which was bookable for one day last August 1st).

All this to show that it is a very grey area indeed for the airlines, such as BA, to tell you that you knowingly booked a fare that was incorrect and therefore your ticket is not valid. En plus, they are so damn profitable that they could easily honour it and earn back a bit of much needed goodwill these days.