The FCO is headed by the Secretary of State for Foreign and Commonwealth Affairs.
The Foreign Office was formed in March 1782 by combining the Southern and Northern Departments, each of which covered both foreign and domestic affairs in their respective geographical parts of the Kingdom. The two departments' foreign affairs responsibilites became the Foreign Office, whilst their domestic affairs responsibilities were assigned to the Home Office.
Construction of the present FCO headquarters began in 1861 as headquarters for the Foreign Office and finished in 1868. They were part of a complex of government buildings inculding also the India Office, and later also the Home Office and the Colonial Office. The Foreign Office was designed by the architect George Gilbert Scott in classical style -- although he had wished it to be Gothic -- and Lord Palmerston, the then Foreign Secretary. Over the years these offices became increasingly cramped due to increasing staff numbers and much of the fine Victorian interiors was covered over, especially after World War II. In the 1960s demolition was proposed, but due to a public outcry asserting their heritage value the buildings were retained and extensively refurbished.