X24 on display at the Royal Navy Submarine Museum
|Preceded by:||V class|
|Succeeded by:||XE class|
|Subclasses:||X3, X4, X5-10, X20-25, XT|
|Lost:||7 (5 scuttled, 1 foundered, 1 collision)|
|General characteristics (X class)|
|Length:||51.25 ft (15.62 m)|
|Beam:||5.75 ft (1.75 m)|
|Draught:||5.3 ft (1.60 m)|
|Test depth:||300 ft (91.5 m)|
|Armament:||2 × 4,400 lb detachable amatol charges|
Known individually as X-Craft, the vessels were designed to be towed to their intended area of operations by a full-size 'mother' submarine - (usually one of the T class or S class) - with a passage crew on board, the operational crew being transferred from the towing submarine to the X-Craft by dinghy when the operational area was reached, the passage crew returning with the dinghy to the towing submarine. Once the attack was over, the X-Craft would rendezvous with the towing submarine and then be towed home. Range was limited primarily by the endurance and determination of their crews, but was thought to be up to 14 days in the craft or 1,500 miles (2,400 km) distance after suitable training. Actual range of the X-Craft itself was 500 nmi (930 km) surfaced and 82 nmi (152 km) at 2 knots (3.7 km/h) submerged.
The craft was about 51 feet (15.5 m) long, 5.5 feet (1.68 m) in maximum diameter and displaced 27 tons surfaced and 30 tons submerged. Propulsion was by a 4-cylinder Gardner 4LK  42 hp diesel engine, converted from a type used in London buses, and a 30 hp electric motor, giving a maximum surface speed of 6.5 knots (12 km/h), and a submerged speed of 5.5 knots (10.1 km/h). The crew initially numbered three—commander, pilot and ERA (Engine Room Artificer, i.e. engineer) but soon a specialist diver was added, for which an airlock, known as a wet and dry compartment, was provided. The ERA, usually a Navy Chief Petty Officer, operated most of, and maintained all of, the machinery in the vessel.
The weapons on the "X-Craft" were two side-cargoes - explosive charges held on opposite sides of the hull with two tons of amatol in each. The intention was to drop these on the sea bed underneath the target and then escape. The charges were detonated by a time fuse.
A number of development craft were built before it was felt that a feasible weapon had been produced. The first operational craft was HMS X3 (or HM S/M X.3), launched on the night of March 15, 1942. Training with the craft began in September 1942, with HMS X4 arriving in October. In December 1942 and January 1943 six of the "5-10" class began to arrive, identical externally but with a completely reworked interior.
The operational base and training establishment was HMS Varbel at the former Kyles Hydro Hotel at Port Bannatyne on the Isle of Bute in the Inner Hebrides of Scotland. Their first deployment was Operation Source in September, 1943, an attempt to neutralise the heavy German warships based in Northern Norway. Six X-Craft were used, but only 2 successfully laid charges (under the German battleship Tirpitz); the rest were lost, scuttled or returned to base. Tirpitz was badly damaged and out of action until April 1944.
This was the only multiple X-craft attack. The lost craft were replaced early in 1944 with X20 to X25 and six training-only craft.
On April 15, 1944 HMS X24 attacked the Laksevåg floating dock at Bergen. X22 was intended for the mission, but had been accidentally rammed during training and sunk with all hands. The X24 made the approach and escaped successfully, but the charges were placed under Bärenfels, a 7,500 ton merchant-vessel along the dock, which was sunk; the dock suffered only minor damage. On September 11, 1944, the operation was repeated by X24, with a new crew; this time the dock was sunk.
X-Craft were involved in the preparatory work for Overlord. Operation Postage Able was planned to take surveys of the landing beaches with HMS X20, commanded by Lt KR Hudspeth, spending four days off the French coast. Periscope reconnaissance of the shoreline and echo-soundings were performed during daytime. Each night, X20 would approach the beach and 2 divers would swim ashore. Soil samples were collected in condoms. The divers went ashore on two nights to survey the beaches at Vierville-sur-Mer, Moulins St Laurent and Colleville-sur-Mer in what became the American Omaha Beach. On the third night, they were due to go ashore off the Orne Estuary (Sword Beach), but by this stage fatigue (the crew and divers had been living on little more than benzedrine tablets) and the worsening weather caused Hudspeth to shorten the operation, returning to Dolphin on 21 January 1944. Hudspeth received a bar to his DSC.
X24 is the only remaining intact example of an X-Craft. It can be found in the Royal Navy Submarine Museum.
X-craft and crews
- X3 — was lost on 4 November 1942 in Loch Striven due to a leaking engine valve. All crew escaped by utilizing their Davis Submerged Escape Apparatus.
- X5 — unofficially named Platypus, commanded by Lt. Henty-Creer RNVR (also the operation's commander), crew S-Lt. Nelson, Midshipman Malcolm, and ERA Mortiboys; passage crew Lt Terry-Lloyd (commanding), L/S Element, Stoker Garrity. Henty-Creer, Nelson, Malcolm, and Mortiboys were killed in the attack, though X5's exact fate is unknown.
- X6 — named Piker II, commanded by Lt. Donald Cameron, crew Lt. J. T. Lorimer, S-Lt. R. Kendall, and ERA Goddard; passage crew Lt Wilson (commanding), Leading Seaman McGregor, Stoker Oxley. Cameron earned a VC, Lorimer and Kendall DSOs, Goddard a Conspicuous Gallantry Medal.
- X7 — unofficially named Pdinichthys, commanded by Lt. Basil C. G. Place, crew S-Lt. R. Aitken, Lt. Whittam, and ERA Whiteley; passage crew Lt Philip (commanding), Leading Seaman J. Magennis, Stoker Luck. Vessel was scuttled immediately following the Tirpitz attack, but only Place escaped before she sank. Aitken escaped from the bottom of the fjord, but Whittam and Whiteley were unable to escape before their air gave out. Place also earned a VC, Aitken a DSO, while Philip earned an MBE;
- X8 — commanded by Lt. McFarlane RAN (Lt. Smart was passage crew commander)
- X9 — commanded by Lt. E. A. Kearon RNVR; A.H. Harte (Able Seaman) and G. H. Hollet (Stoker). Foundered on 16 September 1942 while under tow from the SYRTIS. X9 was unofficially named Pluto
- X10 — unofficially named Excalibur, commanded by Lt. Hudspeth RANVR
The numbering sequence of the X class began with X3 because the designations X1 and X2 had already been used previously - X1 had been a one-off submarine cruiser design from the 1920s while X2 had been assigned to a captured Italian submarine.
- X5 — built by Vickers Armstrong, Barrow-in-Furness, used in Operation Source, sunk Altenfjord 22 September 1943
- X6 — built by Vickers, used in Operation Source, scuttled Altenfjord 22 September 1943
- X7 — built by Vickers, used in Operation Source, scuttled Altenfjord 22 September 1943, salved 1976 for museum restoration
- X8 — built by Vickers, used in Operation Source, scuttled in North Sea 17 September 1943
- X9 — built by Vickers, used in Operation Source, foundered under tow in North Sea 16 September 1943 with all hands
- X10 — built by Vickers, used in Operation Source, scuttled in North Sea 3 October 1943
- X20 — built by Broadbent, Huddersfield, used in Operation Gambit
- X21 — built by Broadbent
- X22 — built by Markham & Co., Chesterfield, collided with HMS Syrtis and lost with all hands while training February 7, 1944
- X23 — built by Markham, used in Operation Gambit, sold 1945
- X24 — built by Marshall, Gainsborough, attacked Laksevåg floating dry dock at Bergen, hulked 1945
- X25 — built by Marshall, sold 1945
- Training craft
- X24 - the only one to have seen service and survive is at the Royal Navy Submarine Museum, Gosport
- The remains of two XT-class craft are present on the beach at Aberlady Bay in East Lothian, Scotland. They were towed there in 1946 and moored to a large concrete block at the low tide level and were used as targets for aircraft. Much of the structure remains, semisubmerged in the sand, and can be reached at low spring tides.
This class of submarine was later featured in the 1968 movie Submarine X-1 starring James Caan as a Canadian Royal Naval Volunteer Reserve officer who after losing his submarine and fifty crew members in a battle with a German ship during World War II, gets a second chance training crews to take part in a raid using midget subs.
- HM Submarine X1 - World War 1 submarine.
- HM Submarine X2 - Name given to the Italian Submarine, Galileo Galilei, after she was captured and taken into service by the Royal Navy.
- XE class submarine - Improved X Class submarine.
- Stickleback class submarine - Improved XE class submarine, in service in the 1950s.
- "Submarine Casualties Booklet". U.S. Naval Submarine School. 1966. Retrieved 2009-09-08.
- Grove, Eric. Sea Battles in Close-up: World War 2, Volume 2 (Shepperton, Surrey: Ian Allan, 1993), pp.124 & 128.
- Grove, p.127.
- Grove, p.124.
- Grove, pp.127 & 128.
- Magennis earned a VC in the midget submarine attack on Takao. Grove, p.127.
-  Supplement to THE London Gazette, p.996 of the article or p.4 of the PDF file
- Grove, p.128.
-  Supplement to The London Gazette, p.996 of article or p.4 of PDF file
- Above Us The Waves by C. E. T. Warren and James Benson - George G. Harrap & Co. LTD - 1953 - ISBN 1-84415-440-8
- Submarines in Colour by Bill Gunston - Blandford Colour Series - Blandford - 1976 - ISBN 0-7137-0780-1
- Submarines - The History and Evolution of Underwater Fighting Vessels by Anthony Preston - Octopus Books - 1974 - ISBN 0-7064-0429-7
|Wikimedia Commons has media related to British X class submarine.|
- Model X-Craft site (in Italian)
- XT-class painting with specification
- Bute at War (detailing the Isle of Bute's unique role during World War II, including the X-craft attack on the Tirpitz)
- Training of Submarine Crews at Tavay Island, Keose
- Cutting cables has cross section diagram of X class submarine and images of construction and launch
- HNSA Ship Page: HMS X-24
- Max Shean Daily Telegraph obituary of X-Class commander and diver