The Hornets of Sea: The World War One Coastal Motor Boats of the Royal Navy | History Hit

The Hornets of Sea: The World War One Coastal Motor Boats of the Royal Navy

Steve Mills

05 Oct 2019

Bill Bremner, Geoffrey Hampden and Eric Anson were junior naval officers who saw the military potential of the fast launches that had competed in the pre war competitions such as the International Harmsworth Trophy.

They collaborated with John Thornycroft who’s Basingstoke company had constructed some of these competition boats. Out of this liaison a new class of fighting boat was born.

The Coastal Motor Boat

Fast and small, with 18 inch torpedoes in their stern, these new World War One Royal Navy ‘Coastal Motor Boats’ (CMB) were not the benign craft their name suggests. High powered and with a single step hull design, they were light, fast planing boats easily transported and when underway, capable of crossing minefields and skipping over protective booms.

Deploying the torpedo from the CMB while planing at speed towards the target with bow high out of the water was the most obvious design difficulty these innovators encountered. This was solved by launching the torpedo tail first out of the stern of the CMB, remembering to then turn sharply out of its way.

To achieve reasonable range and speed required lots of heavy fuel so the boats themselves had to be light; flimsy wooden ‘eggshells’ the crews called them. In August 1916 the first of these 40 foot CMB’s were completed at Platt’s Eyot on the Thames and went into service.

A photo of a CMB travelling at full speed.


Other than their torpedo ‘stings’ in their tail, the CMBs only armament consisted of a few Lewis machine guns. Reliant on speed and surprise, their operations were generally secret and usually undertaken at night.

They proved so effective that production of larger 55-foot boats carrying two torpedoes, or one torpedo and four depth charges, followed these initial successes. 70 foot mine-laying CMBs followed and in 1918 a Cruiser was converted to carry six 40 foot CMBs.

Another major development of CMB technology followed the trials in 1917 of the Royal Flying Corps (RFC) ‘Aerial Target’ drone aircraft. Five Distance Control Boats (DCB) were built, three by converting the 40 foot CMBs Number 3, 9 and 13.

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These unmanned DCBs, designed to be packed with an explosive charge, were remotely controlled from ‘mother’ aircraft using the RFC’s control system. They were tested successfully during 1918.

A 1920 Admiralty review identified the invention of DCBs and Wireless Controlled Aircraft as significant threats to the Royal Navy’s capital ships.

As the CMB fleet grew in numbers and diversity of design during the war, their crews fought with great valour in what were usually secret operations.

At wars end – the new war

At the end of the Great War many countries were vulnerable to Bolshevik influence and aggression as the Russian Civil War raged on their borders. It is not surprising therefore, that in 1919 CMBs would be at sea again engaging this new enemy. CMBs were transported to the Baltic and even to the Caspian Sea.

A coastal motor boat arrives by rail at Baku. 1919.

Operation Red Trek in 1919 involved a British fleet including CMBs in operations in support of the Baltic states. For their actions in attacks undertaken by this fleet, three CMB crew members won the Victoria Cross.

With his experience supplying the Russian Imperial forces with material through their Arctic ports, Gus Agar had been selected by MI6 to operate CMB4 and CMB7 in the northern Baltic Sea to support land based agents.

Attempts to use his CMBs to extract the operative ST-25 (Paul Dukes) from his mission in Petrograd failed but these incursions into the Bolshevik harbours inspired an unauthorised attack.

Sinking the Oleg

Despite its forts, searchlights, formidable minefields and a submerged invisible breakwater, on the night of the 17 June 1919, Agar in CMB4 ran the gauntlet of these obstacles to torpedo and sink the cruiser Oleg. For this action he won the VC which became known as the mystery VC as security demanded Agar’s identity be protected when the Russians put a price on his head.

Following this successful June raid on Kronstadt harbour the aircraft carrier HMS Vindictive and more CMBs joined this Baltic operation and a more extensive attack was instigated against the Russian fleet at Kronstadt on 18 August 1919.

Firing party for dead pilot, deck of HMS Vindictive, Baltic 1919.

This involved Vindictive’s aircraft and eight CMBs attacking at high speed in two waves of three boats in the dark congested harbour while Gus’s boat CB7 guarded the entrance and the remaining CMB attacked the guard destroyer Gavriil. Three boats were lost with many of the crews injured, killed and captured.

William Hamilton Bremner (1894-1970) commanded CMB79A. He was badly injured and spent six months as a POW. He, like many others on this raid were decorated. Tommy Dobson who commanded the CMB flotilla aboard CMB31BD and Gordon Steele of CMB88 were awarded VC’s.

Bill’s continuing naval career merged into intelligence work in SIS/MI6 through into the Cold War era.

Of the others mentioned……

A group of Naval VC’s at a party given for holders of the Victoria Cross by King George V at Wellington Barracks. Gordon Charles Steele is second from the left and Augustus Agar is in the centre.

Geoffrey Cromwell Edward Hampden (1883-1951) went on to raise a number of patents including one on a Hydrofoil craft. Around 1938 he had serious financial troubles and then his son was killed near Narvik flying a Swordfish aircraft from HMS Furious in April 1940.

George Frederick Vernon Anson (1892-1969) returned home to New Zealand where he had a long and distinguished medical career.

Paul Henry Dukes (1847-1930), MI6 codename ST-25, escaped into Latvia and was knighted in 1920.

Augustus Willington Shelton Agar VC (1890-1968) on the 40 foot CMB7 acted as pilot for the flotilla on the August raid.

In his long naval career he experienced first hand the vulnerability of ships to air power as Captain of the heavy cruiser HMS Dorsetshire when she was sunk in April 1942 by Japanese aircraft. His injuries curtailed but did not end his service days.

Claude Congreve Dobson VC (1885-1940) achieved the rank of Rear-Admiral by the time he retired in 1936.

Gordon Charles Steele VC (1891-1981) also had a long naval career, retiring in 1957.

CMB9 / DCB1 was returned to the water after 40 years following her restoration by its dedicated owners Robert and Terri Morley (see image) and has since appeared at many events including the Queen’s Diamond Jubilee Pageant.

CMB9 returned to the water. Image Credit: Robert Morley and Liner Lookout Cafe.

The RFC’s ‘Aerial Target’ and DCB radio control systems are in the IWM stores. CMB4 is a static exhibit in the IWM at Duxford.

Steve Mills had a career in engineering design and development until he retired, after which he has been involved in the work of a number of organisations. His engineering background in aviation on civil and military projects here and in North America has been put to use over the last 8 years as a volunteer at Brooklands Museum in Surrey.

His book, ‘The Dawn of the Drone‘ from Casemate Publishing is due to publish this November. 30% discount for readers of History Hit when you pre-order at Simply add the book to your basket and apply voucher code DOTDHH19 before proceeding to checkout. Special offer expires 31/12/2019.

Steve Mills