[1][2] Parkinson joined the Colonial Office as a clerk in 1909, marking the beginning of a 36-year career in the British Civil Service.
[3] During the First World War he served with the King's African Rifles and was awarded an OBE in 1919 for his service in East Africa.
He then served as Permanent Under-Secretary of State for Dominion Affairs, but was soon recalled to the Colonial Office after his successor there, Sir George Gater, was transferred to the Ministry of Supply.
[4] Parkinson's second term as Permanent Under-Secretary of State for the Colonies (1940–1942) coincided with several military defeats during the Second World War, resulting in the loss of various colonies, including British Somaliland, Hong Kong and British Malaya.
He visited the Caribbean and Bermuda in 1942–1943; the Gambia, Nigeria, Kenya, Northern Rhodesia, Nyasaland, Mauritius, Seychelles, Aden and British Somaliland in 1943; and Ceylon and Gibraltar in 1944.