Secret: Mr Coyne said at first the workers did not know what the tunnels were going to be used for and were not allowed to tell anybody what they did or where they worked. He said: 'But then they started moving a lot of equipment in and we realised it was a nuclear shelter. People were nervous and weapons were being stockpiled'. When they were being constructed, the public was informed it was a new underground rail network, which had eventually been shelved