Regulations for the Navy Part IIICentral Regulations · 1957
(1) A Captain may be constituted a Commodore when it may be deemed expedient. A Commodore shall, as a general rule, receive an appointment as a Captain of the ship in which his broad pendant is hoisted, and shall not have a Captain of the same ship under him unless specially authorised.
(2) If transferred to another ship temporarily, it shall not be necessary for a Commodore to have an appointment to such ship; but if it be found necessary for him to remain in such latter ship, an appointment shall then be made to the ship in which he is borne.