What inspired the vacuum tube train near the end of Kingsman: The Secret Service...was it the Scientific American article by L.K.Edwards 50 years ago? The one buried under New York made a brief appearance a few years ago in a Godzilla movie.
When I saw the film I took it to have been inspired by Mail Rail. This is the system under London that used to carry mailbags between the major rail termini and the Sorting Office at Mount Pleasant.
This was originally a pneumatic system:
but later became a driverless electric railway - and no longer pneumatic:
The system was closed a few years ago and has now become one of London's more unusual tourist attractions. You can ride on one of the old electric wagons, converted to take a couple of passengers.
A bit of disclosure; I wrote some of the software that controlled the electric system when it received an upgrade in the early 1990s.
The pictures are on the linked website