Artwork for a poster. Subject: Mail Rail. Artist: Rethi, Lili. Media: Paper on board, poster paint, watercolour [?] The Post Office Underground Railway Ð Mail Rail Ð silently and industriously ran under the streets of London largely unnoticed for more than three quarters of a century. But since 2003, the worldÕs first driverless, electrified railway has laid dormant with just a handful of engineers to maintain it. Under new plans developed by the British Postal Museum & Archive, that could all be about to change. As part of a £22m scheme to deliver a new, national postal museum in Central London, the British Postal Museum & Archive is planning on opening up a section of Mail Rail to the general public for the first time in its history.