Given Charles George Duff's age of 36 by May 1940 (assuming 1904 Birth Year) is it feasible He would have been with the BEF, on the Front Line, in France by that time, and later evacuated from Dunkirk ?
ADD: The BEF started moving to France from the 4th September 1939, hence why most Regular Army and Territorials do not appear on the published to view, 1939 Register.