When the son married in 1944, he recorded his deceased fathers occupation as M. D.
Was he inventing that?
I can think of a few possibilities for the meaning of MD. - medical doctor? musical director? managing director?
.?
When Charles Mc Guinness signed the 1921 census, in my opinion, his elegant signature belongs to one who is well educated, confident, and familiar with signing.
Added - worth noting the 1944 marriage was in the Corpus Christie Church, Westminster. Roman Catholic.