The collection covers four decades of correspondence, primarily between Mary and her mother, Mrs Kesteven. The earliest surviving items are occasional letters from Mary at school in the 1920s. The main correspondence sequence begins in the mid-1930s when Mary was married to Christopher Rhodes. In regular communication, the two women record their lives and activities, express their opinions on books and art, comment on the impact on their lives of developments such as rationing, and discuss friends and family, particularly members of the wider Courage family whom Mary saw often. The letters exchanged during and immediately after the Second World War have particular interest, revealing the different experiences of their daily lives in England and in Switzerland. The letters between 1940 and 1948 record Mary's life with Jacques B. Brunius.
Occasionally the correspondence includes letters between Mary's partners and her mother, or letters from other friends or relatives sent as enclosures. The collection contains four series:
Letters written by Mary Barron to her parents, 1927-1930 and 1935-1967 (MS 626/1);
Letters written by Mary 'Molly' Kesteven to her daughter, 1939-1942 and 1951-1967 (MS 626/2);
Letters written by Horace Sidney Kesteven to his daughter, 1939-1942 (MS 626/3);
Family tree showing descendants of Robert Courage (1830-1893), Edward Courage (1832-1904) and Henry Courage (1840-1902), and notes on the earlier history of the Courage family; word-processed documents, n.d. [1970-1992] (MS 626/4)