In this section I will examine the Classification of ships in the Royal Navy. This is worth some attention when trying to explain the somewhat convoluted naming conventions used during WW2 and post war when the Royal Navy sought to standardise ships into respective roles.

This is complicated because politics often have a part to play in naming conventions, for instance between the wars it was considered that the description of a ship as an "Escort Vessel" was too provocative to foreign powers to use.

The RN system is not the only one of course, Australia for instance tends to follow the US system and it's Type 12 ships have always been classed as Escort Destroyers, a classification the RN has only ever briefly flirted with on occasion.

So briefly then let me take a wander through naming conventions in the Royal Navy.


Send a Gunboat!
A Cadmus Class Sloop HMS Fontaine, 1903.
Sloops and the larger Corvettes did not survive long into the 20th century as the Dreadnought and the Destroyer took over.


In the days of sail the typical Sloop was a fore and aft rigged vessel with a single jib. The only difference between a Cutter and a Sloop technically was that a Sloop had a jib stay: a rope from the bow to the jib masthead. Usually a merchant Sloop would be single masted.

The Sloop-of-War was a small warship which could be rigged in any number of ways, typically a Sloop-of-war would have two or three masts and it carried 18 cannon or less in the Royal Navy. The two masters were generally classed as a Brigantine Sloop, or just "Brig". The three masters were technically referred to as "Ship Sloops" and were often square rigged, the French termed them "Corvettes."

As steam took over sail a Sloop came to mean a sea going gun boat capable of acting independently. Carrying 100-200 crew and captained by a Commander (as opposed to a Lieutenant on a Gun Boat and a Captain on a Corvette and above), they would typically displace 1,000 tons and mount 6 x 4" guns.

After the outbreak of WW1 there was a critical need for Fleet minesweepers. The German tactics of sowing mines and attempting to lure British forces on them meant converted trawlers were not adequate. The Sloop was reinvented, but now equipped with mine sweeping gear as well as guns.

In 1917 with little prospect of further Fleet action after the Battle of Jutland and in the face of crippling losses to Submarines many Sloops were equipped with depth charges and used as convoy escorts, some were disguised as merchant ships to lure U-Boats to the surface to be sunk, these were designated Q-Ships.

Between the wars Sloops continued to be built, increasing in size and capability they at first were again primarily Fleet Mine Sweepers and colonial gun boats until the threat of the U-Boat was finally realised and they swapped mine sweeping gear for depth charges. But they were over engineered and could only be produced in small numbers during the war.

The Sloop, as a class, ceased to be after June 1947 when all Trade Protection Ships were redesignated Frigates; Sloops, Corvettes and some Destroyers were re-classified.

In the late 50's the Sloop was to make a come back in the shape of the General Purpose single screw Tribal Class ship, the last of the colonial gunboats. But falling ship numbers and a need to keep up Frigate numbers committed to NATO meant they were re-classified during build as Frigates.

Replica of the American Sloop USS Providence

HMS Cyclamen
Typical of the Flower Class Sloops built during WW1 (not to be confused with the Flower Class Corvettes of WWII)
These ocean going mine sweepers and gunboats proved ideal escort vessels for convoys of merchant ships.
Post WW1 design however specified increasing speed with the use of turbine engines to enable them to keep up with the Fleet, but this meant they could not be produced in the numbers needed when war broke out.

HMS Starling - WWII Sloop


The Corvette was a French invention; they were a small Frigate, flush decked with about twenty cannon. Primarily designed as blockade runners they were too small to be effective fighting ships in the deep water Royal Navy, but captured vessels were put into service as dispatch ships and scouts.
After the Napoleonic Wars the Corvette class fell into disuse in the Royal Navy and did not make an appearance again until the advent of the steam and screw powered ships. Corvettes were built at about 1,800 tons with 12 x 4" guns and in many ways took the place of Frigates which had become massive and armoured and re-classed as Cruisers.

But early in the 19th century the last of the Corvettes were phased out as Destroyers replaced them.

Early in the second world war there was an urgent need for an Escort Vessel that could be mass produced. The new type of ship - the new Flower Class - were classed as Corvettes in a reversal of the former rule as they were now smaller and less well armed than Sloops.

A larger version of the Flower was produced later in the war, the Castle Class Corvette, a few of these were kept in service after the war but were re-classified as Frigates, the Corvette ceased to be a class in the RN post WWII, though it is used in other Navies to signify a small Frigate, often built for insurgence suppression work.

Technically the Captain Class Frigate built post war was a corvette, it had many of the WWII corvette features: single screw, dedicated anti-submarine and purpose designed to be built in non-military yards. But political pressures to maintain Frigate numbers meant it was given the undeserved title of a Frigate.

HMS Calliope
Last of the sailing Corvettes 2,779 tons

HMCS Snowberry
The 980 ton mass produced Escort that came to symbolise the fight against the U-Boat in WWII. The resurrected classification would not survive long in the Royal Navy.


Originally Frigates were flush deck oared galleys operating in the Mediterranean. The French adopted the term to classify a small warship where all the guns were located on a single deck.

The trend during the wars between Britain and Europe had been to build bigger and bigger ships with massed artillery. It was the French who began to produce smaller vessels with high manoeuvrability that could scout for the main fleet, and even harass Ships of the Line, these were the Frigates.

One, the Tygre, was captured by the British in 1747, it was armed with 26 x 9pdr cannon on a single covered deck. The design of the Tygre was copied and the Royal Navy built two of it's own Frigates, The Lyme and the Unicorn.

Design went slightly different from then on, the British increased the size of subsequent Frigates from 581 tons (Lyme) to Endymion in 1797 which displaced 1277 tons. The French kept their own Frigates smaller, faster and more manoeuvrable. This was mainly due to the roles they were meant for, Frigates in the British Fleet were not tied to a Fleet, they acted as scouts and as warships in their own right, and their value as convoy escorts became such that Nelson was to complain that a lack of Frigates was jeopardising his ability to guarantee trade.

With the advent of armour Frigates further increased in size and capability and were termed "Armoured Cruisers" to reflect their role as independent warships rather than as Fleet Scouts as Frigate tended to imply. The term Frigate fell into disuse early in the 19th century along with the Corvette and the Sloop.

The classification was re-introduced during WWII to signify the larger class of Escort Vessels built to replace the Flower Class Corvettes, though the exigencies of war meant the Flowers were retained in service as well. Frigates were long range Escorts whose primary role was anti-submarine. But as the war progressed and the submarine threat was largely defeated the need shifted for anti-aircraft escorts, Anti-Submarine ships were re-equipped as Anti-Aircraft Frigates. The distinction from Destroyer was primarily speed and the slower Escort Destroyers like the Hunt Class were re-classified as Frigates also.

In June 1947 the Admiralty decreed that any vessel whose role was Trade Protection (eg Escort Vessel) was to be classed as a Frigate.

The next shift in naming seemed to occur without any actual decree. Destroyers had been fast Escort Vessels able to keep up with a Fleet, usually torpedo armed, but not always. Post war the requirement for faster Frigates to keep up with submarine development caused many Destroyers to be refitted as Anti-Submarine ships, these were re-classified as Frigates. By the 60's the RN phased out Anti-Aircraft Frigates and combined the function of Anti-Submarine and Anti-Aircraft in the Leander Class, but their primary role was stated as Anti-Submarine. The speed advantage of the Destroyer had now been largely lost and design differences were now that the Destroyer was primarily Anti-Aircraft and the Frigate Anti-Submarine.

Few Navies retain the Frigate Class, the French is one, but includes what most Navies now classify Destroyer. The British type of Frigate is usually designated as a Destroyer Escort (DDE) by other NATO Navies.

By the time the Batch III Type 22 was built, a ship which many (including their crews) thought should be classified as a Cruiser, Admiralty dogma was that the ship's primary role was Anti-Submarine, therefore they were Frigates.

A replica of HMS Rose, a frigate of 24 guns, built 1757, 500 tons

HMS Warrior, entered service in 1861 as a Frigate but was later re-classified an Armoured Cruiser. 26 x 68 pdr 10 x 110 pdr guns, 9,210 tons.

HMCS Antigonish, River Class Corvette of WWII were classified as Frigates though they still carried the Corvette pennant K. 1,370 tons, 2 x 4" guns and 10 x 20mm they carried 150 depth charges and a Hedgehog Projector. Essentially a Frigate was a Sloop without Turbine engines.

HMS Llandaff, A Type 61 Frigate, launched 1955, her primary role was Anti-Aircraft, designed to track enemy aircraft and direct carrier borne aircraft to intercept. Since her role was Escort Vessel she carried a Frigate pennant of F.
2,350 tons, Twin 4.5", twin 40mm guns and two Squid Mortars. Speed 25 knots.


The first Torpedo Boats were so called "Spar Torpedo" armed. Essentially a high explosive ram fitted to a small boat which would attack a larger vessel by charging at it and detonating the ram. It is difficult to imagine the crew of such a boat surviving such an attack!

However the self propelled torpedo was developed, much to the alarm of Naval powers. In the Chilean Civil War of 1891 and the Sino-Japanese war of 1894-1895 small fast boats armed with self propelled torpedoes were used. The design of the Torpedo Boat is largely accredited to John Ericsson, a Swede who immigrated to America and pioneered the use of propellers and fan assisted engines. He is more commonly known as the designer of the USS Monitor.

Well aware of the potential threat to it's Battleships the RN developed the Torpedo Boat Destroyer. These were similar to Torpedo Boats, but armed with guns, they were intended to form a defensive screen around a Battleship, but since they needed to keep up with the Fleet they had to be much larger to give them endurance.

The first Destroyers were HMS Havoc and HMS Hornet, launched in 1893 they had the same distinctive turtle back shape bow as a Torpedo Boat. The class was copied by Britain's ally, Japan, but the Japanese added torpedoes as well and in 1904 used them to attack the Russian Fleet at Port Arthur.

The effect was not as conclusive as was thought at the time, with most of the damage being caused by confusion rather than torpedo strikes, but the attack gave rise to a myth of the Torpedo as a certain giant killer and prompted a scramble to build both Torpedo Boats to attack and Torpedo Boat Destroyers to defend. The fear of torpedo attacks dictated tactics in WW1, Jellicoe having been advised by experts that 50% of all torpedoes launched against his Battleships would hit. The perceived need for defensive Destroyers meant very few were ever released for convoy escort duties.

By WWII the Destroyer was still primarily a combination of gun and torpedoes to act in either role and very much a Fleet defence, too valuable to risk as merchant escorts. There was also the problem that Destroyers were built for speed and were ill suited to the slow plod of a merchant convoy, both in sea keeping at low speed and fuel usage.

Prior to WWII starting the Hunt Class Destroyer was conceived, a scaled down Destroyer which would serve as an Escort. The main difference between the Hunts and the Sloops of the time was speed, the Hunt had a 10 knot advantage. But they were designed to fight the same coastal war of WW1, they had not the endurance for long range escorts and did not figure greatly in the Battle of the Atlantic. The Hunts would be re-classified as Frigates.


A 19th century Spar Torpedo Boat, when men were made of iron!

HM Torpedo Boat 95, the turtle bow was a common feature of the time.

HMS Hunt was a modified design of a Torpedo Boat, armed with guns instead of torpedoes to defend against them.

HMS Kelly, a typical WWII era destroyer, 2,330 tons full loaded, armed with 4 x 4.7" guns, 1 quad 2 pdr Pom-pom, 2 x quad 0.5" machine guns, 2 x 5 torpedo 21" torpedo tubes.

Pennants and Flag Superiors and Classes and Types

This subject seems designed to cause a headache! By 1914 Royal Navy ships were identified by Pennants, flags flown to identify themselves, this comprised a letter which was termed the "Flag Superior" since it flew uppermost, followed by a number. Smaller ships had their Pennant painted on the hull.

Unfortunately Pennant numbers kept changing, perhaps to confuse the enemy or more likely because administrators love swapping filing systems around.

Flag Superiors do not correspond to Class letters, except by coincidence. Destroyers in particular from the First World War tended to be classed by letter for each "run" of building, the letter was incremented in much the same way as car registration plates are. Hence from 1903 to 1905 a series of destroyers were built named after rivers and were Class "E", and they would be termed either as E Class or River Class after their names. But their Flag Superior would be D, H or P. With the outbreak of WWI all destroyers became "F" but later "G" was added as an option and then "H" and "D". Sloops and Escort Destroyers were identified by "U" from 1940, prior to that they had been "L",

During WWII "K" was introduced for Corvettes.

Post war the system was overhauled and Flag Superiors standardised so that each represented a single Class of ship:


Aircraft Carrier
Hydrographic Vessel
Amphibious Warfare
Fast Patrol Boat

HMS Leeds Castle, a WWII Castle Class Corvette sports her post war F for Frigate Flag Superior.

This system came into force in June 1947, prior to that the "F" classification was only seen on Destroyers, Frigates would be L or K. Some destroyers were reclassified as frigates.

It is worth noting that although an official Admiralty edict defined a Frigate as any vessel designed for, or converted to, trade protection; there was no such decree as to what constituted a destroyer. From a torpedo boat killer it had become a torpedo carrying warship, but post war surface torpedoes were largely regarded as obsolete. Destroyers came to be any ship whose primary weapon system was Anti-Aircraft.

The Class system still exists, following the convention that ships in a given class will (usually) have names along a similar theme. "V" class Destroyers for instance all began with "V" and Battle Class destroyers were named for battles. But the system does break down, sometimes for political reasons. The Invincible Class aircraft carrier should have followed the wartime class: Invincible, Illustrious, Indomitable; but the last was instead renamed Ark Royal before launch owing to the huge popularity of the previous two carriers by that name.

But to clarify the different types of Escort Vessels a Typing system was introduced, this was a list of pre-ordained numbers which were assigned to each new class of Escort and designated it's primary role. The system was rendered obsolete when the Royal Navy shrank and it was no longer feasible to have specialised Escort ships, but nevertheless it is still used today for Destroyers and Frigates.

Type Number


Type 11-40 Anti-Submarine


Diesel Powered ASW Frigate on Type 61 Hull - Cancelled


Steam powered high speed Frigate (Whitby, Rothesay, Leander)


Steam powered high speed second rate Frigate (Captain Class) (Emergency Class)


Converted WWII Destroyers


Partly converted WWII Destroyers


Third Rate ASW Frigate (Corvette) - Cancelled


Semi-Conversion of WWII hulls - Cancelled


42 knot turbine Frigate - Cancelled


Gas turbine commercially designed and built Frigate (Amazon Class)


Towed Array gas turbine Frigate (Broadsword, Brave and Cornwall Classes)


Gas and Diesel stealth Frigate (Duke Class)


Commercial version of Type 23 - Cancelled

Type 41-60 Anti-Aircraft


Diesel Anti-Aircraft Frigate on Type 61 Hull (Leopard Class)


Gas powered area defence Destroyer (Sheffield Class)


Improved Type 42 Destroyer - Cancelled


European Common new generation Frigate - Cancelled


Type 42 Replacement (Daring Class)

Type 61-80 Aircraft Direction


Diesel powered Aircraft Direction Frigate (Salisbury Class)


Aircraft Direction Frigate on WWII Destroyer Hulls - Cancelled

General Purpose


Gas and Steam single shaft Colonial Patrol (Tribal)


Gas and Steam Aircraft Carrier Escort (Bristol Class) - Cancelled after first of class

Post WWII the RN drew up a wish list of ships, the Type System, this identified the projected roles of Escort Ships which were to be a major part of the modernised Royal Navy. This list has been added too over the years but when first drawn up it envisaged a comprehensive and balanced escort fleet. Intriguingly the number 13 was omitted from the list.

TYPE 11- Long Range anti submarine Convoy Escort similar to the River and Loch Class Frigates.

TYPE 12 - Fast anti submarine hunter killer, similar to the Bird Class Sloops

TYPE 14 - Dedicated small and cheap anti-submarine escort, similar to the Castle Class Frigates.

TYPE 15 - Destroyer hulls converted to fast dedicated ASW Frigates to provide submarine screens for Carrier Groups.

TYPE 16 - Destroyers equipped with ASW weapons to provide Escort in hostile air, surface and sub-surface environments, similar to the Hunt Class

TYPE 17 - Coastal anti-submarine patrol, similar to Flower Class Corvette

TYPE 18 - Conversion of larger Destroyers such as the Battle Class into ASW Frigate with heavy gun armament

TYPE 41 - Anti Aircraft Convoy Escort, similar to Bay Class Frigate

TYPE 61 - Conversion of Destroyers to radar pickets (changed to Type 62 when the Type 41 was re-designed as a picket)

TYPE 81 - Colonial Gunboat with good all round capability, similar to Bird Class Sloop.

Types 11, 12 & 41 were to share the same hull design, but the convoy escorts would be powered by diesels, this would double their range and give a top speed of 24 knots and excellant low speed economy. The Type 12 needed a speed of 30 knots, the holy grail speed for Fleet Operations, at the time there were no suitable diesels to provide it and the new gas turbines that were becoming available were considered too untried and expensive. In the end a steam plant was chosen but this caused some painful compromises, for a start the standard hull was lost as the Type 12 needed more space to fit even the smallest unit that could be designed, and all pretence of providing damage survivability was lost as to get the compact design both boilers were together and both engines, and they shared adjacent machinary rooms.

The Type 11 was abandoned for a simple and brutal fact that had applied between all wars: there are no convoys in peace time and a ship designed purely to protect them could not be maintained in the face of financial cuts. The Type 12 was chosen to full both Fleet and Convoy protection, cruise turbines were added to improve low speed economy to enable them to serve better as Convoy Escorts at need. Both Types were twin screwed.

The Type 12 and 41 shared a hull that while not interchangable was designed to be pre-fabricated and quickly assembled. A similar but smaller hull was used to manufacture the Type 14, this was a single shaft ship with two boilers, effectively a cut down of the fit on the Type 12, they were fast and highly manouverable and it was intended that three would be built for every Type 12 which would act as a Flotilla Leader for them. In the event the program was cut short for the same reason as the Type 11 was still born, as dedicated anti-submarine vessels they could not serve in any other capacity, with the RN restricted on ships and man power even the relatively low cost Type 14 could not be justified in peace time.

The Type 41 had a short run and then was modified, her armament was reduced in favour of additional radar and radio gear so that she could act as an aircraft direction frigate, the hybrid ship was re-classed as Type 61. But without the speed to operate with the Carriers whose aircraft she was supposed to direct they became something of a white elephant and spent most of their career on foreign stations.

Instead a number of Battle Class Destroyers were adapted to fast aircraft direction ships, these were the Type 62, although oddly the Type number was never officially applied to them.

The Type 15 & 16 destroyer conversions went ahead, largely covering the design and development period needed for the Type 12, they would be gradually phased out in the 60's & 70's as more Type 12's were built to replace them.

The Type 17, intended as an even smaller Type 14 never made it off the drawing board, the Type 18 destroyer conversion was axed in favour of arming new Destroyers with Anti-Submarine helicopters.