Diaries written by Powles while in Kenya between 1928 and 1969, mainly covering his time as Estates Manager for the Howard de Waldens. During Powles' Army service (1939-1944), his wife Barbara stood in for him at Kitale and continued the diaries.

The diaries provide a record of his life and work, in public affairs as well as in connection with the extensive Howard de Walden interests in Kenya. These came to include eight large farms, blocks of land in Sabatia, Athi River, Kapiti Plains, and elsewhere, and a controlling interest in the Upper Nairobi Township & Estate Company and in the East African Standard group of newspapers. The later volumes are of particular interest because Powles was in contact with most of the leading figures in public affairs in Kenya during the post-war years.

Two letters written by Mr Powles in 1968 to archivist P.A. Empson are included in MSS. Afr. 1121 (1.1). The first outlines his career as Estates Manager to the Howard de Waldens, father and son, for whom the diaries were written, and gives his reasons for leaving Kenya in May 1963. The second lists some of the Government and Local Government Committees and Boards on which he served between 1934 and 1963.

MSS. Medit. s. 18 contains papers that came into the possession of Powles through a member of his family who had worked in the East India Company. They are records concerning the Plague of Malta in 1813.