Wonderful Lamson tube system at Heathrow, with addressable collars read by some electromagnetic gismo which would change the "points" in the tubing, there being 4 or 5 possible addresses. Hours of fun sending tubes loaded with punchole confetti to the tower at very busy times....desktops covered with the stuff. System was maintained by two characters we called Tweedledee and Tweedledum who seemd to have a full time job clearing faults.
I think it was Derek Jenkins who told me a story about a cigar being put down a tube at Luton one Christmas.......