[2] Gustav Mayer married Flora Wolff (1882–1962) on 26 October 1905, which afforded him a degree of financial independence and enabled him to resign from his staff job with the newspaper.

He embarked on a career that initially combined work as a private tutor with freelance journalism, but he soon turned to full-time scholarship,[6] devoting himself to the study of the German Labour Movement, basing himself first in Heidelberg and later in Berlin.

[2] Although he made a point of not joining any political party,[7] four years of war left Mayer's interest in the unfolding history of the labour movement undimmed.

Despite his undoubted academic qualities and the support of Hermann Oncken, when it came to a vote by the evaluation committee, the dissertation that he submitted to the Philosophy Faculty of Berlin University in 1918 failed to earn him the hoped for habilitation qualification.

[8] In 1936, Gustav Mayer spoke only broken English so that there was no question of obtaining an academic teaching post, but in London he was able to become a staff member of the International Institute of Social History (IISH).

[8] In later years, Mayer himself on various occasions lamented in writing the paralyzing impact of his bafflement as his family faced the application of anti-Semitic dogmas once the Nazi party took over the government of Germany.

[4] Their younger son, settled in England, abandoning his first name Ulrich and becoming known as Philip Mayer, obtaining a doctorate from Oxford and building a career as a social anthropologist with his wife Iona whom he married in 1946.