Colchester Zoo. DS was obsessed with going on the land-train there so off we went. Crowds, hot day, waiting for the train. He saw the first one leave and had a moment, cried his eyes out and shouted at DH, straining at his backpack, then when the next one arrived, there wasn't room for us on that either.
I had a quick word with the driver and he said, no problem, get into the last carriage. It was guards only, but also had a wheelchair / disabled symbol painted on it.
The train stopped in the lemur enclosure for a five-minute encounter break. DS refusing to leave the train with grim expression
but the driver came all the way back to tell us that if he wanted us to, he would let us all in by another door so that we didn't have to wait or experience crowds again. Really reassured DS that he wouldn't move the train without him.
I asked his name and have emailed the zoo to thank him.