 A 3 @.@ 25 @-@ mile ( 5 @.@ 23 km ) semi @-@ circular network of tunnels was dug beneath northern Ramsgate , connecting to the existing railway tunnel . It was opened by the Duke of Kent on 1 June 1939 , three months before the outbreak of war , and visited during the war by Winston Churchill . The network was capable of sheltering 60 @,@ 000 people , although Ramsgate 's civilian population at the time was approximately 33 @,@ 000 . 
