In the mid 1960s he was intimately involved in writing the constitution of Barbados, prior to the island's independence from the United Kingdom (UK).

In Marshall's time at Hull he is reputed to have refused to accept the poet Philip Larkin's resignation as university librarian.

Larkin's reason for tendering his resignation was his apprehension that his technical knowledge was not adequate to cope with the changes in technology affecting how academic libraries functioned.

Marshall refused the request on the grounds that Larkin's "presence on the staff was of material advantage to the university.

Marshall made significant contributions to society in the realms of human rights and race relations.