London Post Office Railway

The London Post Office Railway, widely known as Mail Rail, sits nearly seventy feet beneath the streets of Clerkenwell. This was a private, driverless electric underground system built exclusively to transport letters and parcels across the city, far away from the congestion of street-level traffic. It operated from 1927 until 2003, moving up to four million pieces of mail every day on a miniature track that stretched six and a half miles from Paddington to Whitechapel.