The Foreign and Commonwealth Office came into existence on 17 October 1968 by the amalgamation of the Foreign Office, the Commonwealth Office and the Diplomatic Service Administration Office. Plans for its creation, however, had begun as early as 1962, when a Committee on Representational Services Overseas chaired by Lord Plowden was appointed to review the purpose, structure and operation of the UK's overseas services.
Plowden's report of February 1964 (Cmnd 2276), which was generally accepted by the government, concluded that the division of responsibility for representational functions between foreign and Commonwealth countries, and in the Commonwealth between commercial and other work, had great practical disadvantages. The unified HM Diplomatic Service was therefore created on 1 January 1965.
The government also decided that the Colonial Office (not part of the Plowden Committee's remit) and the Commonwealth Relations Office should be merged, and the resultant Commonwealth Office was formed in August 1966. This was the first step towards the creation of a single ministry to handle all the UK's external affairs, identified as an ultimate aim by Plowden, but not a specific recommendation.
From January 1967 the Commonwealth and Foreign Offices operated a common file registry system, under the oversight of the Diplomatic Service Administration Office. Additionally, there were a number of joint Foreign Office/Commonwealth (Relations) Office departments where staff from both offices provided common services to each. These included joint departments dealing with information research, administration, policy and guidance, overseas police and labour advisers' departments, a joint consular department, and joint departments for nationality and treaty matters, protocol matters, conferences and research.
Responsibility for the Commonwealth Institute was among the functions inherited from the Commonwealth Office. In November 1970 the office absorbed the Ministry of Overseas Development. The Ministry of Overseas Development became the Overseas Development Administration (ODA), a body answerable to the FCO. The former Minister of Overseas Development became a junior minister of the FCO with the title Minister for Overseas Development.
The ODA remained a distinct element within the Foreign and Commonwealth Office and its organisation was largely unaltered. In June 1974 it became a separate department once more with its own minister, but in June 1975 the latter again became Minister for Overseas Development exercising delegated power formally vested in the Foreign Secretary as Minister of Overseas Development. The two departments remained distinct, however.
In 1982, responsibility for the Government Hospitality Fund, which provided hospitality for foreign heads of state and ministers visiting the United Kingdom, was transferred from the personal responsibility of the Chancellor of the Duchy of Lancaster to that of one of the junior ministers of state for foreign and commonwealth affairs.