Editing Pennant number (section)

===Post-1948===
After the Second World War, in 1948, the Royal Navy adopted a rationalised "pennant" number system where the flag superior indicated the basic type of ship as follows. "F" and "A" use two or three digits, "L" and "P" up to four. Again, pennant 13 is not used (for instance the helicopter carrier {{HMS|Ocean|L12|3}} was followed by {{HMS|Albion|L14|3}}).
* A  — auxiliaries (vessels of the [[Royal Fleet Auxiliary]], [[Royal Maritime Auxiliary Service]], and [[Royal Navy Auxiliary Service]], including depot ships, boom defence vessels, etc.)
* C  — cruisers (currently none in service, therefore unused)
* D  — destroyers
* F  — frigate (former escort destroyers, sloops and corvettes)
* H  — shore signal stations (military); survey vessels
* K  — miscellaneous vessels (e.g., the helicopter support ship {{HMS|Lofoten|K07|6}} or the seabed operations vessels [[RFA Proteus|RFA ''Proteus'']] and {{HMS|Challenger|K07|6}})
* L  — amphibious warfare ships
* M  — minesweepers
* N  — minelayers (currently none in service, therefore unused)
* P  — patrol boats
* R  — aircraft carriers
* S  — submarines
* X  — experimental vessels (currently, the only vessel to use this is [[XV Patrick Blackett]] which is not a commissioned ship of the Navy but is crewed and run by the Royal Navy)
* Y  — yard vessels