This is a list of Permanent Under-Secretaries in the British Foreign and Commonwealth Office (and its predecessors) since 1790.
Not to be confused with Parliamentary Under-Secretary of State for Foreign Affairs
Permanent Under-Secretaries at the Foreign Office, 1790 to present
These are the Permanent Secretaries or senior civil servants at the Foreign Office.
References
Permanent Under-Secretary of State for Foreign Affairs Wikipedia(Text) CC BY-SA