 Wartime efficiency measures led to the branch being closed temporarily on 22 September 1940 , shortly after the start of The Blitz , and it was partly fitted out by the City of Westminster as an air @-@ raid shelter . The tunnels were used to store items from the British Museum , including the Elgin Marbles . The branch reopened on 1 July 1946 , but patronage did not increase . In 1958 , London Transport announced it would be closed . Again it survived , but the service was reduced in June 1958 to run only during Monday to Friday peak hours and Saturday morning and early afternoons . The Saturday service was withdrawn in June 1962 . 
