I am an idiot.
Yesterday I was at the local station to buy train tickets into the city for a hospital appointment today. It was much, much later in the day that I realised my appointment is next Thursday, not today. See, I told you I was an idiot.
Not to worry though. I went back to the station today, explained what I'd done and asked to change the tickets. They couldn't do that, but were quite happy to issue a full refund of the £2.50 cost of the tickets. Great, thought I.
Then I was told there would be a £10 fee.
I decided not to go ahead.