The letter is almost a thing of the past since the advent of email, and if it weren't for online shopping it seems postal services would almost be out of business. In fact, in Canada they almost are. In 2013, to offset ongoing losses, Canada Post announced plans to phase out door-to-door deliveries in favor of centralized community mailboxes.
Strange to think then that in London there were once so many letters and parcels that to transport them across the clogged city, special tunnels were built and fitted with trains that operated on narrow gauge tracks. The 23 miles (37 km) of tracks – the actual distance is only a bit over six miles (9.6 km), from Paddington to Whitechapel – transported mail to the major sorting offices of the city. At the railway's peak, trains ran 19 to 22 hours a day, five days a week, carrying 4 million letters a day through the tunnels that are located 71 feet (22 m) below ground.
In 1855 an underground pneumatic tube system was first proposed and in 1863 a pneumatic railway was built, which sucked iron cars along their rails from Euston station to Eversholt Street in a minute. Sadly just a trial, it was discontinued in 1866 due to financial issues. The Post Office Railway Bill was finally passed in 1913 and construction of the railway began in 1914.
London’s traffic was bad even at the turn of the 20th century and being able to ferry the majority of the mail about without dealing with traffic jams made the service far smoother. Using tunnels for transport is still a popular idea today, especially to cut down on time
and traffic. Just look at ideas for a transport tunnel that would take passengers from New York to Beijing in two hours
In 2013, to mark the century since the Bill, the tunnels were the subject of a photo exhibition at the British Postal Museum. In March last year the local council gave approval for part of the Mail Rail to be turned into a ride, with the old seat-less train carriages to be refitted to accommodate passengers. It will open in London next year and will, says the British Postal Museum and Archive, give visitors "the opportunity to explore the hidden world of this railway under Mount Pleasant through an engaging exhibition and interactive ride." However, the length of the proposed trip will only comprise a 0.6 mile (1 km) loop of the original lines.
This is not the only proposed use for some of London’s disused tunnels. Design firm Gensler has suggested turning some of the derelict Tube tunnels into energy-generating subterranean pedestrian and bike paths.