During the Second World War, Cambridge, like most of England, was under threat of aerial bombardment. The first daylight raids over the country took place in June 1940, and they continued throughout the remainder of the war, killing some 40,000 civilians. Though Cambridge itself was not badly hit, the city experienced 424 air raid alerts during which high-explosive bombs, oil bombs, and other incendiaries were dropped, killing 29 people. Some of the city’s residents may have hidden in a concrete air raid shelter built under the green of Jesus College in 1939. Its outlines are an unexpected reminder of the war only recently made visible.