By May 1941 London had suffered almost eight months of continual nightly bombing. Usually raids began  soon after dusk and continued until the early hours of the following morning. A pattern was established with the first big raid on the London Docks and surrounding districts on 7th September 1940. The Luftwaffe came in two waves, the first to saturate an area with incendiaries and high explosive bombs, the second to concentrate on selected targets, aided by the light of fires started earlier. For many Londoners nights spent in a shelter became a way of life. All were exhausted and some, including the London Fire Brigade, had begun  to wonder how much more they could take. The last big raid on London came on the night of 10/11th May 1941 and, overall, it was the heaviest and the worst.
From the very beginning of the war it was clear that the siting of emergency water supplies was essential, particularly in areas of high risk. After the City Blitz on 29th December 1940, both the London Fire Brigade and the London County Council recognised that in addition to those temporary dams erected in many streets, once debris had been cleared, the basements of the bomb damaged buildings could be rendered water-tight and made into ideal reservoirs for extra sources of water. Neither the Home Office, however, who were responsible for financing these operations, nor the Architect's Department of the LCC, who were responsible for carrying out the work, seemed particularly co-operative. Lists of potential sites were drawn up early in 1941 but it was not until after the formation of the NFS, in August of that year, that the work of conversion was significantly completed.
One of these sites, with a peculiar and tragic history of its own, was the site of the Surrey Theatre in Blackfriars Road, on the corner of Waterloo Road and St George's Circus. Known locally and affectionately as the Surrey Music Hall after its conversion to a music hall in 1904, the original Surrey Theatre was built in 1872 as a Royal Circus and 'equestrian establishment' managed by the poet Charles Dibdin. It was burnt down three times, the first in 1799, after which it was rebuilt as a theatre, the second in 1805 and a third time in 1865, during an act of 'drollery' on a 'huge trombone'. In its time it played host to many of the great theatrical acts, including the magnificent 19th century clown, Grimaldi. It is mentioned by Massey Shaw in his work on theatre fires in London. At the beginning of the 20th century it was used as a cinema before its brief life as a music hall and by 1935, after standing empty for a number of years, it was acquired by the London Eye Hospital, which stood adjacent to it at St George's Circus, with the intention of extending its premises to include teaching and research departments.
By the time war broke out in 1939 the Surrey Music Hall had been demolished and the site stood empty. Divisional Officer Blackstone, second in command of the London Fire Brigade Southern Division, was quick to recognise its potential as an additional and considerable supply of water. Without waiting for the necessary authority from the LCC, he organised members of the fire brigade to cement it up and render it water-tight. When full, it held 200,000 gallons of water. The initiative, without having gone through the 'proper' channels, was later declared 'unconstitutional'. In May 1941 it was the site of the second largest loss of fire brigade lives in the London Region.
On the night of 10/11th May in 'F' District, Southwark, fires were started just before midnight. Accounts of that night make harrowing reading. In addition to Southwark Fire Station, a sub-station in Rockingham Street, the policemen's married quarters at the station in Borough High Street, and the local mortuary were also on fire. Borough Market was wrecked by high explosive bombs and a barrage balloon was brought down in Marshalsea Road. In Harper Road the LCC Weights and Measures Office was hit by a land-mine, killing a fire guard and several others. In Southwark Bridge Road a shelter was hit by two high explosive bombs. In Webber Street a shelter was flooded when the sewers nearby burst open and in the early hours of the morning the fire situation at the Elephant and Castle, a major junction leading from the City to the south east, was so bad that shelterers in a shelter near Freeman, Hardy and Willis's shoe shop had to be