* Trigger warning for Londoners: man engages in conversation with fellow commuter on tube. *
The only time I ever had regular conversations with anyone on the tube during my 30+ years living in central London was with a gentleman who worked for the RNIB who was always accompanied by his gorgeous black lab guide dog. I regularly bumped into them on my commute home on the Circle line, and we chewed the cud accordingly.
Then, one day, there was no black lab. It turns out that, as a working dog, the lab was preparing for retirement, and gradually their work is reduced over a number of weeks to acclimatise them to their new regime of, well, whatever retired guide dogs do. The gent still managed to negotiate his way home, which included changing at Tower Hill for Fenchurch St. He said while he could negotiate the journey fine, but without his lab it just took very significantly longer.
So over the next few weeks I got to see the lab less and less, until never again. Meanwhile the gent was on a waiting list for a new guide dog, but it wasn't clear when that would be, as guide dogs don't exactly grow on trees.
Then the pandemic happened, I moved offices, and I've never bumped into him again, but I sincerely hope he did find a new companion.