Isabel was his second wife. She had previously been married to Cyril Graham-Smith, a civil engineer employed in the Indian educational service at Poona. In 1927, Graham Smith filed for divorce, with Wren named as co-respondent. The divorce was granted, and a letter by Isabel to Ronald Colman (who played Beau Geste in the silent film) in 1929 on behalf of her "seriously ill" husband suggests that she and Wren had married at least as early as 1928 (actual date 3 December 1927). "Isobel" was the heroine of "Beau Geste".