Letters from Henn to his brother, Canon Percy V. Henn, in Western Australia on various family matters [originals]. Also, letters to his son John in Kenya, and others (1916-1936), including references to his Chairmanship of the Joint East Africa Board (1926-1929) [photocopies].

Correspondence, notebooks etc. as Chairman of the Joint East Africa Board (1926-1929) and as a representative on the Imperial Economic Committee (1924-1927), the Advisory Committee of the East African Dependencies Trade and Information Office (1925-1935), and the Tanganyika Railway Commission (1930-1931).