Many years ago when we had a folding caravan we were travelling round Wales. We had gone some distance on a hot day and we arrived tired and wanting to go to the loo. The toilet block was not as clean as I would have liked and I walked through, pushing back the doors to try and find a cubicle that looked OK. I pushed back one door and there was a middle aged man sitting on the toilet reading a newspaper. He, quite unabashed, looked up and simply said "Afternoon". I'd mistaken the men's block for the women's block! Thank goodness we had planned to travel on and go to another site and left early the next morning - I would have been so embarrassed to see him again.
I never seem to learn to, as my Dad used to say "engage brain before opening mouth". At a social event a lady said how excited she was to have received her Freedom Pass in the post that morning. Another lady said she didn't look old enough to be eligible for one. I said you only had to be 60 to get the Freedom Pass (London pass). I suddenly realised, from the awkward silence that ensued, that what I was actually saying was "You look 60 but you don't look 65+" - and, on reflection, she probably doesn't look 60 but it was too late to put things right.