‘M’ was the signature of an artist who designed a poster for British Railways.
Information taken from: Anonymous, ‘The Poster Designer and His Problems’, Art and Industry, Vol.35, No.205, July 1943, p.23.
Mass Communications Academic, @MMUBS. British Home Front Propaganda posters as researched for a PhD completed 2004. In 1997, unwittingly wrote the first history of the Keep Calm and Carry On poster, which she now follows with interest.