HMS D1: The Secret Prototype of Britain's First Diesel Submarines

An End to Petrol

By 1907 the Royal Navy had several dozen submarines, and almost all of them ran on petrol. Petrol gave off fumes that poisoned crews and vapour that blew them up, and the boats that burned it had neither the range nor the seaworthiness to go far from home.

What it meant in practice can be read in HMS A9, whose crew were found unconscious at their posts in 1908. Something better was needed, and it already existed. The German engineer Rudolf Diesel's engine ran on heavy oil, which was far harder to set alight and gave off very little dangerous vapour.

The question was whether one could be built small and light enough for a submarine.

Vickers at Barrow thought it could, and the Admiralty ordered a prototype. HMS D1 was laid down on 14 May 1907 and launched on 16 May 1908, in secret, as the Navy did not want other powers to know what it was building. She was completed on 1 September 1909.

A Real Seagoing Submarine

D1 was the first British submarine to be fitted with diesel engines instead of petrol, and that was only the start of what was new about her. She had two propellers instead of one, so that she could manoeuvre and keep going if one shaft failed.

She carried her main ballast in saddle tanks along the outside of her hull, which left more room inside. And she was fitted with a wireless telegraphy set, which meant that a submarine at sea could report what she saw and be told where to go.

The aerial wires strung from her mast can be seen in the photograph at the top of this page. As Historic England put it when her wreck was protected in 2021, diesel propulsion, twin propellers and wireless were the innovations that every later Royal Navy submarine adopted.

Together, they changed what a submarine was for. The A, B and C boats were essentially harbour defence craft, which waited off the ports in case an enemy came to them. D1 and the seven sisters built to her design could go to sea, stay there for days and patrol off the enemy's coast.

In the annual fleet manoeuvres of 1910 D1 is reported to have made her way up to the waters off Colonsay in the Hebrides and "torpedoed" two cruisers of the opposing fleet, a long way from her base at Fort Blockhouse, later HMS Dolphin. Whether or not every detail of that story is right, the point it made was true.

In 1914 it was the D class and the E class developed from it that took the war to the German coast.

A Gallery of Captains

D1 was the prototype, and the Navy gave her to some of its best young submarine officers. In the five years before the war she had at least nine captains. Like B5, she was a school, and some of her pupils went on to extraordinary lives.

Lieutenant David de Beauvoir Stocks had her in 1910, and in 1915 he took E2 into the Sea of Marmara during the Gallipoli campaign. Lieutenant Robert Ramsay, who had her in 1911, went on to be the first captain of M1, the submarine with a battleship's gun.

In 1912 she was commanded by Lieutenant Commander Francis Cromie. In 1915 Cromie took E19 through the narrow Oresund into the Baltic, where the British boats worked with the Russian fleet, and that November he sank the German cruiser Undine.

In 1917 he became the British naval attaché in Petrograd, and he stayed on at the embassy through the Russian Revolution after the ambassador had gone home. On 31 August 1918, when the Cheka, the Bolshevik secret police, broke into the embassy, Cromie met them on the staircase with a revolver and was shot dead.

He remains the only British naval attaché ever killed in action.

One of her last captains, in 1917, was Lieutenant William Maitland-Dougall of the Royal Canadian Navy, the first Canadian naval officer to command a British submarine. He moved on to D3, and on 12 March 1918, on patrol in the Channel off Dieppe, D3 was sighted by a French airship. Her crew fired recognition rockets.

The airship's crew had never been told what the signals meant, thought they were under attack and dropped bombs as D3 dived. She sank with all hands. Survivors were seen in the water but drowned before anyone could reach them. Maitland-Dougall was twenty-three.

The inquiry found that he had acted in the only way possible.

War and the End

By 1914 D1 was the oldest of her class, and she joined the 8th Submarine Flotilla at Portsmouth, with the depot ships Maidstone and Adamant. In the first months of the war she helped guard the Dover coast against a German invasion that never came, and then patrolled beyond British waters watching for German shipping.

In September 1917 she was moved to the Portsmouth local defence flotilla, and a year later she was put on to training.

A few weeks before the end of the war she was taken out of service, and on 23 October 1918 she was deliberately sunk off Dartmouth in Devon, to be used as a target for the ships and hydrophone operators learning to find submarines on the seabed. It was a useful end for her.

The Navy that had built her as a prototype now used her to teach the next generation how to hunt boats like her.

Found by Accident

She lay forgotten for a century. The search that found her started with the U-boat historian Michael Lowrey, who was working on the German submarines lost in the First World War and thought a wreck off Dartmouth might be one of them.

A team of technical divers led by Steve Mortimer went down to look, expecting a U-boat. As Mortimer said afterwards, they were thrilled to discover a ground-breaking British submarine instead.

D1 sits upright and largely intact on the seabed, and in 2021, on the advice of Historic England, she was scheduled as a protected monument. Divers can still visit her, but everything on her must stay where it is.