Seaforth

Coastal Motor Boats

Thornycroft and the Origins of Fast Attack Craft

Authors:	Martin Kelly and David Griffiths
Published:	2025
Format:	Hardback, 256 pages
Size:	268 × 226 × 26 mm

£40⁰⁰

Tax included

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The Birth of the Fast Attack Craft

An in-depth history uncovering Thornycroft’s role in pioneering the Coastal Motor Boat, from WWI innovations to Soviet and global naval influence.

Coastal Motor Boats: Thornycroft and the Origins of Fast Attack Craft challenges conventional naval history to reveal a far more complex story behind the creation of Britain’s fast attack craft.

While the Coastal Motor Boat (CMB) has long been credited to three Royal Navy officers during the First World War, new research based on previously unseen family records shows that shipbuilder John I. Thornycroft played the decisive role. Drawing on his pioneering pre-war work in motorboat racing, Thornycroft laid the technical foundations that made the revolutionary CMB possible.

The authors explore the boat’s intended mission – an attack on the German High Seas Fleet – and explain why it was never carried out. Although early views branded the CMB a disappointment, that perception changed dramatically after the 1919 Kronstadt raid, when CMBs achieved spectacular success against the Bolshevik fleet. For the first time, this account incorporates contemporary Soviet sources that shed new light on these dramatic events.

The book also traces the enduring legacy of Thornycroft’s designs, which influenced naval forces worldwide from Finland to China, and examines the Second World War service of later variants. It concludes with insights from the replica CMB.4 project at Portsmouth Naval Base – an extraordinary example of experimental archaeology revealing the practical challenges and achievements of the original builders.

About the Authors

David Griffiths is the project manager of the organisation that built the CMB replica at Portsmouth. His research focuses on early twentieth-century naval design and engineering innovation.

Martin Kelly is a naval researcher whose interests include espionage and amphibious planning in the early twentieth century and the naval career of Erskine Childers, both central to the story of the Coastal Motor Boats.