Pennant Number - Royal Navy Systems

Royal Navy Systems

The system was adopted prior to World War I to distinguish between ships with the same or similar names, to reduce the size and improve the security of communications, and to assist recognition when ships of the same class are together. Traditionally, a pendant number was reported with a full stop "." between the flag superior or inferior and the number, although this practice has gradually been dropped, and inter-war photos after about 1924 tend not to have the full stop painted on the hull. The system was used throughout the navies of the British Empire so that a ship could be transferred from one navy to another without changing its pendant number.

Pendant numbers were originally allocated by individual naval stations and when a ship changed station it would be allocated a new number. The Admiralty took the situation in hand and first compiled a "Naval Pendant List" in 1910, with ships grouped under the distinguishing flag of their type. In addition, ships of the 2nd and 3rd (i.e. reserve) fleets had a second flag superior distinguishing from which naval depot they were manned; "C" for Chatham, "D" for Devonport, "N" for Nore and "P" for Portsmouth. Destroyers were initially allocated the flag superior "H", but as this covered only one hundred possible combinations from H00 to H99 the letters "G" and "D" were also allocated. When ships were sunk, their pendant numbers were reissued to new ships.

The flag superior for whole ship classes has often been changed while the numbers stayed the same. For example, in 1940, the Royal Navy swapped the letters "I" and "D" around (e.g. D18 became I18 and I18 became D18) and in 1948, "K", "L" and "U" all became "F", where there was a conflict, a 2 was added to the front of the pendant number.

During the 1970s, the service stopped painting pennant numbers on submarines on the grounds that, with the arrival of nuclear boats, they spent too little time on the surface, although submarines do continue to be issued numbers.

HMS Lancaster was initially allocated the pennant number F232, until it was realised that in the Royal Navy, form number 232 is the official report for ships that have run aground; sailors being superstitious, it was quickly changed to F229.