Section 70(1)(b) in The Naval Ceremonial, Conditions Of Service And Miscellaneous Regulations, 1964
(b)At Sea-At the ensign staff whenever possible, but in bad weather or whenever the ensign staff is not available from any cause, such as the ship being cleared for action, and the like, it should be worn :(i)In ships with one mast, on a staff in a suitable position on the after superstructure.(ii)In ships with two masts, either as in (i),or at a small gaff to be fitted as a "peak"on the main mast.