A postman operates an underground mail route control panel in about 1935. By the turn of the 20th century, congested streets and fog meant that mail transported between the main Post Offices and railway stations in London was severely delayed. In February 1911 a departmental committee recommended construction of an electric railway with driverless trains to alleviate the problem. In 1913 the Post Office (London) Railway Act was passed, paving the way for a new railway – six and a half miles long, with tunnels an average of 20 metres (70ft) below ground. It would connect the West End and East End via eight stations. Photograph: courtesy of BPMA