INSIGHT: Snail mail and its underground rail

During the campaign to win votes for women in 1909, two suffragettes posted themselves to 10 Downing Street, hoping to speak to the Prime Minister, Herbert Asquith.

They were delivered by a telegraph messenger boy but officials refused to let them through the door.

This sounds like an urban myth but is related as fact in the new Postal Museum in central London. If you tried to send yourself through the post today you’d probably be told that you were over the weight limit for parcels. But it is now possible to retrace part of the journey once taken by millions of letters by travelling on Mail Rail, the railway that was built beneath London for the Post Office.

A ride on Mail Rail is the highlight of a visit to the Postal Museum. It’s a tight squeeze to get into the carriages. There’s little headroom and the gauge is only 0.6m (2ft). You’re taken on a 20-minute ride below the giant Mount Pleasant sorting office near King’s Cross, with an informative audio-visual display en route. After the trip you can wander into what was once the railway’s maintenance workshop to inspect displays explaining the history of Mail Rail.

In the early years of the 20th century mail taken across London by road travelled at less than 7mph, so it was proposed to build an electric underground railway to transport letters more rapidly. Work on digging the tunnels 20m below ground started in 1914 but was halted by the outbreak of war, and the line was finally opened in 1927.

Speeding things up: moving mail underground meant faster delivery (Credit: The Postal Museum)

The line ran for 6 miles from Paddington mainline railway station in the west to Whitechapel in the east via four sorting offices and Liverpool Street station. Floodgates were installed in the tunnels below Liverpool Street because during construction workers had to flee when water from one of the capital’s underground rivers burst through. But the gates have never been needed to hold back water since the railway began operation.

Chutes and conveyors took mail to and from the sorting offices and mainline stations above. Signal lights regulated the feeding of mail down into the railway. Mail Rail’s underground stations bustled with activity, with 200 staff employed for 22 hours a day.

The electrical systems were designed by chief engineer Herbert Gunton. Driverless trains carrying letters travelled at up to 30mph and were controlled by postal workers at each station using levers on enormous switch frames to change points on the line. The process was computerised in the 1990s and controlled from a central point below Mount Pleasant.

Trains ran on 440V DC supplied by a third rail. An incline was used to slow the cars at each station while the voltage dropped to 150. Back in motion, the trains accelerated down a slope as the voltage went back up to 440.

You can get up close to a maintenance locomotive built in 1927 and once used to deliver equipment and to tow broken-down trains. It was powered by 152 battery cells and worked independently of the mains electricity on the rest of the network.

Before email: letters were transported around London along railway lines (Credit: The Postal Museum)

Also on display is a mock-up of one of the carriages once used by postal workers to sort mail while on long journeys on the mainline railway. Mail Rail fed letters to these travelling post offices at Paddington and Liverpool Street.

The travelling post offices ran from 1838 until 2004 and were immortalised in the 1936 film Night Mail, which depicted the journey from London to Scotland. You can see one of the trackside nets that were used to transfer mail bags from the carriages without the train having to stop.

Eventually it was thought that roads were cheaper than rail for transporting letters, so the decision was made to close Mail Rail in 2003. It was suggested that the redundant tunnels could be turned into a mushroom farm or a cycle highway, but instead part of the network was opened to the public in the new museum.

It’s worth looking out for one further quirky exhibit when visiting: a car once used on a pneumatic tube railway that ran for a short stretch beneath London and carried mail in the 1860s and 70s. The cars were propelled at up to 35mph by air pressure created by a big steam-powered fan. Proponents of the latest Hyperloop schemes might like to see it.

For more details, see: www.postalmuseum.org