flew from London to Tanganyika in 1927 to provide Tanganyika with its first plane
Could this be it? Listed as the first Certificate of Registration. DH 51 VP-KAA registered 3rd Jan 1929, now in the Shuttleworth Collection.
Civil Aircraft Register - Kenya
https://www.shuttleworth.org/collection/dh51-misskenya/
It is stated in the Shuttleworth Collection Records, England, that an aircraft currently in their collection, a de Havilland DH.51, was built in 1925 and shortly after John Evans Carberry bought and shipped it to Mombasa. The DH.51 first flew in Africa on 4 April 1926. In June 1928, Tom Campbell Black, G. Skinner and A. Hughes bought the aircraft and on 10 September 1928, it became the first aircraft to be registered in Kenya. Named Miss Kenya, it was first registered G-KAA, but with the change in the registration system, it was re-registered VP-KAA
https://en.wikipedia.org/wiki/Tom_Campbell_Black