After the crisis, the British Government decided to make these a permanent feature, with a standard design of precast concrete trench lining.

'high-rise bunkers' or blockhouses), were a type of construction designed to relieve the pressure Nazi German authorities were facing to accommodate additional numbers of the population in high-density housing areas, as well as pedestrians on the streets during air raids.

Alternatives had to be found speedily once it became clear that Germany was contemplating air raids as a means of demoralising the population and disrupting supply lines in the UK.

When the Wilkinson's Lemonade factory in North Shields received a direct hit on Saturday, 3 May 1941 during a German attack on the north-east coast of England, 107 occupants lost their lives when heavy machinery fell through the ceiling of the basement in which they were sheltering.

The arches were covered usually with wooden or brick screen- or curtain walls, thus giving a considerable amount of protection against air raids – provided, of course, that railway lines were not the prime target of the attack at the particular time and so being more likely to suffer from direct hits.

None of these concerns had been borne out by experience during the bombing raids of the First World War, when eighty specially adapted tube stations had been pressed into use, but in a highly controversial decision in January 1924, Anderson, then chairman of the Air Raid Precautions Committee of Imperial Defence, had ruled out the tube station shelter option in any future conflict.

Floodgates were installed at various points to protect the network should bombs breach the tunnels under the Thames, or large water mains in the vicinity of stations.

In Stockport, 6 mi (9.7 km) south of Manchester, four sets of underground air raid shelter tunnels for civilian use were dug into the red sandstone on which the town centre stands.

In the United Kingdom, it was being recognised early that public shelters in open spaces, especially near streets, were urgently needed for pedestrians, drivers and passengers in passing vehicles, etc.

The programme of building street communal shelters commenced in March 1940, the government supplying the materials, and being the moving force behind the scheme, and private builders executing the work under the supervision of surveyors.

[18][page needed] At around the same time rumours of accidents started to circulate, such as on one occasion people being drowned due to a burst main filling up the shelter with water.

It was named after Sir John Anderson, then Lord Privy Seal with special responsibility for preparing air-raid precautions immediately prior to the outbreak of World War II, and it was he who then initiated the development of the shelter.

[19][20] After evaluation by David Anderson, Bertram Lawrence Hurst, and Sir Henry Jupp, of the Institution of Civil Engineers, the design was released for production.

When they were buried outside, the earth banks could be planted with vegetables and flowers, that at times could be quite an appealing sight and in this way would become the subject of competitions of the best-planted shelter among householders in the neighbourhood.

[22] The Anderson shelters performed well under blast and ground shock, because they had good connectivity and ductility, which meant that they could absorb a great deal of energy through plastic deformation without falling apart.

However, when the pattern of all-night alerts became established, it was realised that in winter Anderson shelters installed outside were cold damp holes in the ground and often flooded in wet weather, and so their occupancy factor would be poor.

[24] Its design enabled the family to sleep under the shelter at night or during raids, and to use it as a dining table in the daytime, making it a practical item in the house.

[25]Half a million Morrison shelters had been distributed by the end of 1941, with a further 100,000 being added in 1943 to prepare the population for the expected German V-1 flying bomb (doodlebug) attacks.

They were provided with elaborately-concealed underground Operational Bases (OB), usually built by the Royal Engineers in a local woodland, with a camouflaged entrance and emergency escape tunnel.

The shop producing spun-concrete lighting columns ceased production and turned over to concrete air-raid shelters, of which 100,000 tonnes (220 million pounds) were manufactured, principally for the air ministry.

The segments were 510 millimetres (20 in) wide; a pair of them formed an arch 2.1 metres (7 ft) high and transverse struts were provided to ensure rigidity.

Military air-raid shelters included blast pens at airfields for the security of aircrews and aircraft maintenance personnel away from the main airbase buildings.

The German authorities claimed that Hochbunker were totally bomb-proof, but none were targeted by any of the 41 10,000-kilogram (22,000 lb) Grand Slam earthquake bombs dropped by the RAF by the end of World War II.

Two of these bombs were dropped on the U-Bootbunkerwerft Valentin submarine pens near Bremen and these barely penetrated 4 to 7 metres (13 to 23 ft) of reinforced concrete, bringing down the roof.

Among these stand out the Plaça del Diamant refuge as well as air-shelter 307 (Refugi 307), today one of the Barcelona City History Museum heritage sites.

[30] Other cities with extant bomb shelters from the Spanish Civil War include Madrid, Guadalajara, Alcalá de Henares, Santander, Jaén, Alcañiz, Alcoy, Valencia and Cartagena.

The public air-raid shelters are commonly employed as game rooms in peacetime so that the children will be comfortable to enter them at a time of need, and will not be frightened.

A shelter is designed to protect the population in the event of a threat of a possible gas or poison leak, armed attack such as war, radioactive fallout, or the like.

[41] During the pre-WW2 period the Metaxas regime initiated an extensive Civil Defence system designed to protect civilians in the event of enemy bombing.

From 1939 forward virtually all new apartment buildings contained built-in hardened basements and cellars that functioned as (unofficial) bunkers, although these lacked the more sophisticated equipment of the state built shelters.