https://en.wikipedia.org/wiki/London_Pneumatic_Despatch_Comp...
(they were mostly used for packages but engineers travelled using the system as well)
It ran until 1953. Paris also had one. It's a worthwhile read.
They say it is no longer working after the floods of 2002, but the article is from 2004 so what do I know.
My colleagues in that department some times had to crawl 1/4 of a mile in the tunnels to unstick the capsules! - that is why I chose the mathematical modeling section
I was trying to imagine a 1/4 mile crawl in a small tube as an engineer and was just thinking, "NOPE." but if I had built the system and it was near 100% safe, maybe...
"The Edinburgh Evening News reported in 1876 that the trucks containing the parcels continually stuck in the tunnels, and this was the reason for the failure of the company."
Here's a great podcast on a mail system of pneumatic tubes. Definitely worth a listen.