Stratford Central Line tube tunnels were used as air raid shelters. Before the beginning of the Second World War a programme of extensions to various London Transport tube lines had commeced, which had to be put in abeyance in 1939.  The Central Line tunnels east of Stratford had already been constructed but there was no rail traffic. (In fact Gants Hill station further east gave access to the tube tunnels, a considerable length of which was used for an underground factory producing aircraft parts.) The reverse of these passes bears the wording: 'The Holder of this Ticket must agree to accept and abide by such Rules and Regulations as may be introduced at any time by teh Controlling Authority. - West Ham Borough Council'