The following notes were taken from a meeting with the donor, 09 Jul 2015, and as such may include some conjecture. Detailed information about the safari may be found in Colin Sayer's book, "A Royal Safari 1930," which is held in the National Motor Museum's Reference Library.
Herbert Sayer was in charge of Wolseley sales in Bombay, before he was selected to go to Kenya. The team received six cars from England for the trip, with one car already in Kenya.
The cars were state of the art at the time, but were only made from 1929-1931 as an export model (the non-export models were called Counties). Sayer took receipt of six of them in Mombasa. The fact that the cars were on safari was partly advertisement, given the rough terrain, and a number of the documents reveal that Wolseley were interested in whether it was possible to sell the cars in Africa.
Herbert Sayer (information received from donor) :
Pre-war 5/6 years with the Bosch Magneto Co. as technical and sales representative.
1914-15 Royal Naval Air Service (C.P.O.) Motor Machine Guns.
1916-18 Tank Corps. Tank Commander. Technical instructor to tanks and Senior Officers. Created and controlled schools of instruction in France.
1919 War Office. G.S.O.2 Tank Corps. Service in Gallipoli and France and in special solo mission to south Russia.
1919-24 Managing Messrs. John Fowler & Co. (Leeds) Depot in India in succession to Col. Johnson and in association with Mr. Gough.
1925-26 Went to Peru to establish Morris Commercial Cars and Morris Cars.
1927-31 Manager in India for Messrs. Wolseley Motors (1927) Ltd, eventually winding up and closing down their three depots in Calcutta, Delhi and Bombay.
1929-30 Twice toured South Africa for Wolseley Motors to establish distributors, visiting Cape Town, Durban, Johannesburg, Port Elizabeth, East London, Salisbury and Bulawayo. Motored from Cape Town to Rhodesia.
1930 In sole charge of the seven Wolseley cars used throughout the Prince of Wales' safari in East Africa (which passed through Tanganyika, Kenya, Uganda, Soudan and Belgian Congo, as the areas were known at the time).
1931-34 Inaugurated and managed Messrs. Morris Industries (India) Ltd, controlling the wholesale and service interests in India, Burma and Ceylon for Morris Cars, Morris Commercial Cars, Wolseley and M.G. Cars.