Ever spotted one of these drum-shaped buildings along the Northern line?
13 of the distinctive structures lurk close to tube stations. They are relics of the Second World War.
During the early 1940s, eight deep-level shelters were built to protect the population from bombing (seven along the Northern line and one at Chancery lane). Each had two entrances, mostly like the one above.
The shelters could accommodate up to 8,000 people in a pair of parallel tunnels deep beneath the street. Unfortunately, they were not completed until after the main Blitz, so only saw limited use.
The shelters were cleverly designed so that, after the war, they might be linked together to form an express tube line (a plan that had already been mooted before hostilities began). Alas, more pressing needs meant that the money never materialised.
The shelters were never demolished. Most became secure document storage space, but a few have found more imaginative roles.
Here we track down the surface buildings of the eight shelters.
The shelter farthest north is on Haverstock Hill, close to Belsize Park tube station. It's a prominent landmark on the slopes of Hampstead, shining white against the brown-brick buildings.
Like London buses, the entrance buildings always come in pairs. The second is much harder to spot. Peer down the alley next to Costa (north of Belsize tube), and you'll spot the twin, partly covered in ivy.
As with Belsize Park, one of Camden's shelters is easy to find, the other less so. The more prominent can be found on Buck Street, just off the main strip. It's currently decorated with a piece of street art by Nathan Bowen.
The second shelter is very well hidden. It's in a car park round the back of the famous Jazz Cafe, accessed by Underhill Street. Unusually, neither of the pair are whitewashed.
Most readers will have walked past this most central pair of shelters. One can be found on Tottenham Court Road, though it's not obvious — set back from the street, skulking in the shadows.
Its playfellow on Chenies Street is much more prominent. This handsome beast is known as the Eisenhower Centre, a nod to its role in the Second World War. General Eisenhower used the subterranean site as his headquarters during the build up to D-Day. It's now used for document storage.
One of the entrances in Stockwell is hard to miss — surely London's gaudiest war memorial. It's worth taking some time to explore this structure. The paintings, by prolific London muralist Brian Barnes, depict many local heroes, including Violette Szabo and Roger Moore. Nearby, Britain's first statue of an Afro-Caribbean woman (and baby) can be found.
The second entrance is, by contrast, a shrinking violet. It hides away from the main road behind housing, but can be viewed from Levehurst Way.
Of the three Clapham shelters, the northern appears the most dilapidated from the outside. The north entrance, painted green and decorated with silver graffiti, is easy to spot a couple of hundred metres north of the tube station on Clapham Road. The southern entrance lacks a drum-shaped building, and is hidden away in a service yard off Bedford Road. We tried to grab a photo, but got some suspicious looks as we peered through the private gateway. Sorry.
Of all the deep-level shelters, Clapham Common has the most inventive modern use. In 2015, the beautifully punning Growing Underground company installed a subterranean farm within the tunnels. Herbs and salads are now cultivated in its vast hyrdoponics bays.
Few are granted access, but the two entrances are easily spotted on Clapham High Street (one on the junction of Clapham Park Road, the other on Carpenter Street).
The shelter at Clapham South is the only one you're likely to get a look inside. London Transport Museum runs occasional tours as part of its Hidden London programme. This is the shelter that briefly housed Jamaican immigrants from the MV Empire Windrush, back in 1948. The entrances are both obvious. One stands proud on the fringes of Clapham Common. The other, further south, is now covered in glazed tiles and struts out from a housing development like a modernist igloo.
You can see photos from inside the shelter in our earlier article.
And a side-note about Chancery Lane
The deep level shelters follow the Northern line from Belsize Park to Clapham, but a side-branch to St Paul's was also partly constructed. The shelter at Chancery Lane was converted to a telephone exchange after the war. It lacks a drum-shaped surface building, but there are other signs if you know where to look. These include a wood-lined ventilation shaft on Leather Lane (above), and this distinctive building at 39 Furnival Street.