Reference.....
Mr. Carter
The procedure for signing despatches is laid down
in Diplomatic Service Procedure Volume 1, Section D 3.
Subsection (5) reads as follows:-
Despatches to all Heads of Missions should be signed by an officer of Grade 4 (or an officer deputising as such) or above. His signature should be written below the words "(for the Secretary of State)". In the Commonwealth Office constitutional and ceremonial considerations require that despatches to Governors-General and Governors should ordinarily bear the signature of the Secretary of State and this is normally appended in facsimile.
Mitha sh
(J. K. Marsh)
24 September 1969