Transparent Pneumatic Bank Tubes

Yesterday I was temporarily imprisoned in a bank. Apparently this happens a lot, and arises from the location of faulty ATMs in completely public spaces, so opening the machine involves the exposure of thousands of quid, which they don't want to go missing, so they lock everyone in.

[po] has helpfully suggested that a solution to this would be to ensure that the backs of ATMs are always sited in private areas of the bank. This strikes me as an entirely practical and good idea, but not very picturesque.

Therefore I propose that ATMs situated on the outside wall of the bank be linked to a vault via tough transparent overhead pneumatic pipes. When a customer types in her PIN and requests cash, a signal is sent to the basement where a safe containing piles of notes and a fan constantly agitating them opens a hatch through which the requisite notes are wafted and blown through the tubes through the bank foyer into the machine itself. If a statement or slip is required, it is printed inside the safe, folded into a paper aeroplane using mechanical hands and flown through the tubes to arrive in the customer's hands. The notes are of course carefully counted before being dispensed.

Customers and staff inside the bank can divert themselves by watching the activity in the tubes.

This would also mean that the actual cash is safely situated in the basement and that the ATM itself contains little of monetary value, rendering it more secure.