London’s Lost Tunnels
In recent years there have been numerous concerning incidents involving rail tunnels and construction works that have highlighted the need for environmental vigilance. One of these occurred in March 2013 when the driver of a First Capital Connect train from Moorgate to Welwyn Garden City reported that water was flowing from the roof of a rail tunnel between Old Street Station and Essex Road Station on Network Rail’s Northern City Line. Moments later a piling rig’s auger broke through the cast iron lining of the tunnel below and landed on the tracks below. In February this year (2016), contractors drilled a hole through the roof of a London Underground tunnel just outside Shepherds Bush Station. These two incidents occurred on known underground tunnels, but what about the lost tunnels from days gone by that cross the capital?
Amongst the hundreds of miles of tube tracks and railway lines lies a forgotten railway – the Royal Mail rail tunnels.
The Royal Mail’s ‘secret’ railway was the first driverless electric railway in world, with trains running for nineteen hours a day deep beneath the choked streets of central London, transporting mail safe from traffic and weather. 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 were severely delayed. It was suggested the construction of the ‘Mail Rail’ was required and by 1913 the Post Office (London) Railway Bill was passed as an Act.
The Mail Rail, which opened in 1927, once transported four million parcels and letters a day along a network of 6.5 miles on 2ft gauge-lines, approximately 21 metres below the streets of London. The line ran from Paddington Head District Sorting Office in the west to the Eastern Head District Sorting Office at Whitechapel in the east, with eight intermediary stations along the route:
Construction of the tunnels started in February 1915 from a series of shafts using the Greathead Shield System. Civil Engineer James Henry Greathead, “the father of the tube”, and once a pupil of Peter W. Barlow, made a significant contribution to the early tube network by developing a tunnelling shield that greatly speeded up the tunnelling process.
The first successful tunnelling shield, a device that has been used in one form or another in almost every major tunnel built during the last 180 years, developed by Marc Brunel was based on a shipworm – a mollusc that shovels pulped wood into its mouth then excretes a hard brittle residue that lines the tunnel it has excavated, rendering it safe from predators. Brunel’s design was improved and adapted by Peter W. Barlow in the course of the construction of the Tower Subway and then by James Henry Greathead for the City and South London Railway – known today as the Northern Line.
Greathead’s shield incorporated Barlow’s cylindrical design and sharp steel blades with the use of compressed air and the addition of cast-iron rings to line the tunnels – adopted by today’s modern tunnel boring machines.
Groundsure’s Energy and Transportation report provides a comprehensive search of existing and planned energy and transport infrastructure. The report includes HS2 data, Crossrail 1 and 2 route and active and historical railways and tunnels. Click here to find out more.