HMS/m D1


Heritage Category:
Scheduled Monument
List Entry Number:
Date first listed:
Location Description:
1 nautical mile south-east of the eastern Blackstone, off Dartmouth, Devon.


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The building or site itself may lie within the boundary of more than one authority.

Location Description:
1 nautical mile south-east of the eastern Blackstone, off Dartmouth, Devon.
National Grid Reference:


The wreck comprises the remains of HMS/m D1, a submarine commissioned into the Royal Navy in 1909. Built by Vickers at Barrow-in-Furness, HMS/m D1 was the prototype for the D-class, which were designed as the first submarines intended for long range offensive operations. On the 23 October 1918 HMS/m D1 was expended and scuttled as a target during trials of submarine detection equipment.

Reasons for Designation

The wreck of HMS/m D1, located approximately 1 nautical mile south-east of the eastern Blackstone, off Dartmouth, Devon, is scheduled for the following principal reasons:

* Rarity: The wreck is a unique prototype of the D-class submarine, and is a rare survival of a pre-1914 submarine;

* Survival: The wreck is in a remarkable state of preservation and in an almost complete state, including fixtures and fittings. The remains of the D1 are the most intact known D-class submarine within English territorial waters;

* Potential: HMS/m D1 has considerable potential to inform on the design process of early submarines through the survival of in situ machinery and fittings, together with plans for both HMS/m D1 and later D-class submarines;

* Documentation: Technical plans, historic photographs, logs and reports of trials comprehensively document the construction and career of HMS/m D1. More recently, geophysical and diver survey data provide an up to date archaeological record of the wreck; * Vulnerability: The component parts of the submarine and its fixtures and fittings remain vulnerable to uncontrolled salvage.


Built by Vickers at Barrow-in-Furness, HMS/m D1 was the prototype for the D-class, the Royal Navy’s first diesel powered submarines. HMS/m D1 was launched in strict secrecy in May 1908, and commissioned in September 1909. The D-class was a significant development on the earlier C-class, and was considerably larger, with almost double the submerged displacement. The D–class was intended to operate in an offensive role beyond coastal waters, as opposed to the defensive coastal operations undertaken by the earlier classes. The D-class contained several innovations that would become integral parts of subsequent Royal Navy submarine types and formed a prototype for the majority of British patrol submarines which saw action during the First and Second World Wars. Key developments in construction included the introduction of external main ballast tanks, diesel propulsion, twin propellers, vertically set twin bow torpedo tubes, a torpedo tube at the stern and the installation of a wireless telephony system which allowed the submarine to both transmit and receive signals.

The potential of the D-class was demonstrated during training exercises in 1910 when the D1 successfully torpedoed two of the opposing fleet’s cruisers during a training exercise off the Scottish coast, demonstrating the submarine’s capabilities to operate a long distance from its home base.

Eight submarines of the D class were constructed. HMS/m D2, HMS/m D3 and HMS/m D6 were sunk outside English territorial waters, while HMS/m D4, HMS/m D7 and HMS/m D8 were sold and scrapped in 1919. The wreck of HMS/m D5 is located off Lowestoft, Suffolk, and was assessed for designation under the Protection of Wrecks Act 1973 in 2016. The wreck of HMS/m D5 was not designated on account of the absence of surviving features on the pressure hull. Subsequently the wreck of HMS/m D5 was designated under the Protection of Military Remains Act 1986 in 2019.

At the outset of the First World War HMS/m D1 was assigned to the 3rd and 4th Submarine Flotilla at Dover for use as a local defence craft. It was subsequently moved to the 8th Submarine Flotilla in September for offensive operations. HMS/m D1 remained with the 8th Submarine Flotilla throughout 1914-1916, with the exception of a brief posting to Dover with the 4th Submarine Flotilla. In October 1914, HMS/m D1 undertook a patrol into the mouth of the river Ems in order to monitor German shipping movements, and received a mention in dispatches for coming into contact with the enemy during patrol operations in the Heligoland Bight. In late 1916 HMS/m D1, along with other D-class submarines, joined Platypus’s Flotilla, based at Killybegs, County Donegal. In September 1917 HMS/m D1 joined the Portsmouth Local Defence Flotilla until March 1918, after which it was relegated to training duties. On the 23 October 1918 HMS/m D1 was expended and scuttled as a target during trials of submarine detection equipment.


The wreck was first charted by the UKHO in 1920. Divers identified the wreck as a complete and intact submarine in 1989 and suggested it may be the remains of UB113. Subsequent reinterpretation has suggested the wreck was in fact the remains of UC49. Both of these proposed identifications were disproved by the results of the 2018 investigation, as the combination of two forward torpedo tubes, single stern torpedo tube, two propellers and single rudder are not found on UBIII class and the UCII class submarines. The overall dimensions and the shape and position of the conning tower, torpedo tubes and deck fixtures are consistent with the technical plans of HMS/m D1.

The diving investigations in 2018, along with the interpretation of geophysical data revealed that the wreck appears to be intact and in good structural condition. It sits upright on a flat seabed at a depth of approximately 50m. The inner pressure hull and the outer hull retain their shape and coherency, and the ballast saddle is largely intact. The main body of the wreck is exposed. The lower hatch on the conning tower is open, and it is apparent that this section of the pressure hull is filled with sediment, although other sections of the wreck are free of sediment. The bow of the submarine is partly buried in the seabed.

An area of 75m within 50.33283, -3.49948 (WGS84) forms the protected area.


Books and journals
Akermann, P, Encyclopaedia of British Submarines 1901-1955, (1989)
Evans, A S, Beneath the Waves: A History of HM Submarine Losses [1904-1971], (1986)
Wessex Archaeology (2020) HMS/m D1, Lyme Bay, Devon, Desk Based Undesignated Site Assessment (214390.14)


This monument is scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. This entry is a copy, the original is held by the Department for Digital, Culture, Media and Sport.

End of official listing

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