When her father died in 1906, her mother took May and her brother Audley (1903–66) to live in Bedford, England.
In 1919, she matriculated at Somerville College, Oxford, where her tutor in history was Maude Clarke.
She graduated with a Bachelor of Arts (BA) degree, and then taught in a school for one year.
[1] She was a lecturer in medieval history at the University of Liverpool from 1927 to 1935, before returning to Somerville College, Oxford in 1936 as fellow and tutor.
In 1955, she left Oxford having been appointed Professor of History at Westfield College, University of London.