Deep Level Shelter Tunnels
Note: You can see many of the features described below in a modern day tour of a deep level shelter I partook in on 19th March 2004 along with another visit to Clapham North deep level shelter made on 12th December 2006.
As congestion on the Northern Line increased in the '30s, a plan was developed to build a second pair of tunnels in parallel with the Charing Cross branch of the Northern Line that would act as an express route through London. These plans were shelved at the outset of the Second World War, but as the platforms of the Underground became increasingly used by the general public overnight as air raid shelters (despite being initially discouraged), work began in 1940 on building deep level shelters which were envisaged to eventually become the platform tunnels for the express route.
The stations on the Northern Line with shelters
Ten shelters were originally planned - five to the north of the Thames and five to the south. All of these were to eventually form part of the Northern Line express route apart from Chancery Lane and St. Pauls, which were associated with the Central Line. The stations on the Northern Line that were equipped with extra tunneling are: Belsize Park, Camden Town, Goodge Steet, Stockwell, Clapham North, Clapham Common, Clapham South. Work on St. Pauls was abandoned in 1941 for fear of damaging the cathedral's foundations and also work ceased on a shelter at Oval soon after, due to extensive flooding. It is unknown whether Oval would have been included in the express route.
Above ground, each shelter's shafts were protected by specially constructed 'pill box' buildings to prevent any bombs that directly hit the location from going underground. Each pill box housed lift machinery and provided the cover for spiral staircases down to the shelter's tunnels.
3D layout of a typical deep level shelter
Each shelter consisted of two parallel tunnels that were 16ft 6in (approx. 4.9m) in diameter and were 1400ft (approx. 427m) in length. Two pairs of shafts were sunk for each shelter, with the pairs being sited a distance from each other in case a bomb struck, blocking a shaft. At each location, one shaft was for the spiral staircase and lift, the other a narrower ventilation shaft.
The two tunnels were interconnected at various places along their length. A floor was constructed at the horizontal diameter level of the tunnel, providing two decks of accommodation. Ventilation, medical, and catering facilities were provided and electricity was obtained from two sources in case bombing caused one to fail - the local authority and the London Underground system, which had its own power station at Lotts Road.
The spiral staircases were constructed in the form of a double helix. One staircase would lead to the upper deck, the other to the lower. This was to allow shelterers to be able to quickly access their destination deck with minimum confusion. On the whole, the upper and lower decks were run independently, though access between decks was provided in the mid-point and at both end of the tunnels. The lift would have access to both upper and lower decks, but was not meant to be used by shelterers.
Toilet facilities were constructed near the lift shafts, with the sewage being periodically hydraulically pumped up a rising main to a sewer close to surface level. There was storage capacity of 5 days for sewage should the hydraulic mechanism fail for some reason. Water was supplied from the local water supply, but should this fail, each shaft was equipped with a 3000 gallon tank of water near the surface.
Each shelter was originally designed to house up to 12,000 people but by the time they were built, the number of bunks had been dropped to a more comfortable 8,000. Bunks were arranged along the walls in various configurations, to maximise use of space.
Ventilation is vital in such a confined environment and a lot of thought was given to this. Air entered the shelter through the entrances and flowed down the spiral staircases, along the connecting tunnels into the shelter area. Stale air was then sucked out of the shelter through metal pipes in the roof (top deck) and under the floor (bottom deck). A fan pumped the air up a specially constructed ventilation shaft, out into a 30ft high tower so that it exhausted well away from the fresh air entering at ground level. When the fans were run at maximum power, the air in the shelter would be completely changed 15 times an hour.
The air was filtered in case of gas attack. All doors were gas seals when closed, and should there be an attack, the entrance doorways would be shut, with the air passing through grilles in the roof of the pill box (clearly visible on the Goodge Street picture below) and through gas filtration equipment.
It was hoped that when their wartime use had come to an end, tunneling would re-start to allow the already constructed tunnel sections to be interconnected, providing the express Northern Line route. For this reason, most shelters were constructed with ease of access to the existing Northern Line in mind. All of these shelters were constructed close to and in parallel with the existing platform tunnels of nearby stations on the Northern Line, and have interconnection tunnels with the existing platforms. In some cases, these interconnections have since been blocked.
Cross section of shelter and Underground platforms at Goodge Street
Use During the War
Most of the shelters took about a year and a half to complete, but amazingly, the government got cold feet about using them as public shelters as they were incredibly expensive to maintain. Several of the shelters were re-purposed. Goodge Street became Genereal Eisenhower's headquarters, some were converted for government use while others were used as army barracks, to house troops in transit.
It took the advent of the flying bombs (V1 and later V2) to convince the government that they should be used as they were originally intended and some were converted back to be used as public shelters.
After the War
After the Second World War came to an end, plans to create the express route stayed on the shelf, and were then ultimately dropped as money for the project wasn't available. Most of the shelters found post war use initially as accommodation for the army in transit and most are today in use as storage facilities.
As they were now being used for other purposes, all the deep level shelters were isolated from their associated active Underground stations, in most cases the interconnection tunnels being bricked up.
Belsize Park deep level shelter being used for document storage. In places, the original World War Two bunk beds are now used as shelving.
The deep level tunnels at Goodge Street have had a particularly interesting history; during the Second World War, they were equipped as General Eisenhower's headquarters and since then they have been used as an army transit camp until a serious (but non-fatal) fire closed the camp on the night of May 21st 1956. Officials were alarmed by the fire and deep level shelters were no longer considered suitable for accommodation.
Since then, several of these tunnels have been used to store archived material with Goodge Street's tunnels now being used to store films and video tape.
One of Goodge Street's pill box entrances has been smartly decorated by the company currently in occupation and it has been named The Eisenhower Centre in in memory of the American President who used it as his Second World War command centre (Yes, that's spelt correctly though arguably it should be "center" as he was an American :-) ).
On 19th March 2004, I visited Belsize Park deep level station to see what has survived from the tunnel's war time era. It's surprising how little has been removed in the 50 years since they were last used as shelters and interesting to see how its current occupier has creatively adapted some of the original fixtures for their own use.
Follow me for a virtual tour of Belsize Park deep level shelter, as it is today! Alternatively click on the... thing below, which we discovered in one part of the complex!
On December 12th 2006, I and a small group of people local to Clapham were given the rare opportunity to visit this site shortly before it was leased out for doccument storage. Unlike Belsize Park, this location has been stripped bare and was completely empty so provided a fascinating opportunity to see the tunnel infrastructure and how it was put together.
Find out more about what we saw and to see a significant new collection of pictures that I took on the visit, including many presented at a higher resolution than I normally use on this page!
Other Deep Level Structures
A similar plan to provide an express route was envisaged for a stretch of the Metropolitan Line between Earl's Court and Mansion House. Again this was abandoned though part of the project was incorporated into the stretch of the Piccadilly Line between Earl's Court and South Kensington. An abandoned platform tunnel still existed for years as the only tangible vestige of this project at South Kensington whose locked entrance can still be seen through a ventilation grille on the west bound Piccadilly Line platform. The tunnel itself has since been lost when the escalators were built and the doorway now effectively opens onto a wall.
Last modified: December 19th 2006