District officer

The District Officer (abbreviated to D.O.), was a commissioned officer of one of the colonial governments of the British Empire, from the mid-1930s also a member of the Colonial Service of the United Kingdom, who was responsible for a District of one of the overseas territories of the Empire.
Role.
The district officer was an administrator and often also a magistrate and was the link between the professional and technical services of the colonial government and the people of his district. He was at the heart of colonial administration throughout most of the British Empire, although not in British India, where the same functions were carried out by members of the Indian Civil Service, nor in the self-governing Dominions.
District Officers wore uniforms, according to the climate, but their formal tunic with gold braid was usually reserved for ceremonial occasions.
Until the 1930s, each overseas possession had its own administrative service, and prospective District Officers needed to apply to one or more of them. Once in post, an officer wishing to transfer to another colony or British protectorate had to make a new application to its government. However, in the 1930s a unified Colonial Service was created, with a number of sub-services, and each of its officers was a member of the civil service of a particular territory and also of one of the sub-services of the Colonial Service managed by the Colonial Office, based in Whitehall.
Career progression.
Before being appointed, a candidate was first a District Officer Cadet, undergoing a rigorous training, and was then promoted to Assistant District Officer, usually after two years of successful probation and after passing examinations. On being appointed as a District Officer, he took on the administration of a District, usually in the territory of the Empire where he was.
Because of the number of districts, many District Officers remained in the same role until leaving the Colonial Service. If they were promoted, they became first District Commissioners, then Provincial Commissioners. Some rose to the pinnacle of being colonial Governors, although men were also appointed as Governors whose previous careers had been in other services. In particular, the Governors of Hong Kong, Gibraltar, Malta, and Bermuda were almost invariably senior British Army or Royal Navy officers.