J. & W. Dudgeon were shipbuilders on the Thames. The company passed through several hands, eventually becoming a large complex of oil storage tanks, but retaining Dudgeon's name. Amazingly they survived the Blitz and continued operations until 1951. When the site was being demolished a fire broke out and resulted in the largest loss of life within the UK’s fire service since WW2.
Fire teams arrived and, believing the fire to be out, they put a curtain of water into the open top manhole of tank 97. It is believed that this pull of water drew air into the tank, mixing with the flammable vapours. It was then decided that in order to ensure there was no further fire, the bottom manhole should be opened. Unable to find a spanner to undo the nuts, they tried to burn them off. As soon as a workman applied the cutting flame to the first nut, the vapours inside the tank ignited, blowing the roof off the tank, and killed five firemen and a demolition worker. This website gives much more information about the history of the site.
From Red Plaque: "The Dudgeon’s Wharf disaster led to a new code of practice for UK firefighters when removing tanks with flammable substances. It also helped to bring about the Hazchem Code, the now well-known visual signage of dangerous and volatile substances contained in all buildings, vehicles and storage areas lorries. Introduced in the 1970s, the Code makes it simpler for firefighters to identify and tackle dangerous chemicals during incidents, protecting themselves and the public."
Credit for this entry to: Alan Patient of www.plaquesoflondon.co.uk