Beginning at midnight on the 13th August 1961, East German police and army began to close the border with West Berlin. The barbed wire and mesh barrier that was constructed overnight was gradually replaced with a virtually impregnable ring of reinforced concrete that ran 155km around West Berlin.

The border between East and West Germany – sometimes referred to as the inner-German border – had been closed since 1952, although the crossing between East and West Berlin remained open. This easy access proved highly problematic for the Communist government of East Germany, since people comparing the two parts of the ...