Coastal Motor Boat 4

The original batch of Coastal Motor Boats (CMBs) were designed and constructed in 1916 by John I Thornycroft and built at Platt’s Eyot at Richmond on the River Thames. The War Department’s specification was for a fast, shallow-draught boat, capable of passing through a minefield and then delivering a single 18-inch Whitehead torpedo. ‘Coastal Motor Boat’ was a camouflage term for the boat, so as to not give away its true purpose.

CMB 4 took part in raids on Zeebrugge and Oostende but, most famously, in two raids on the Bolshevik fleet in June and August 1919. In the first daring raid, the cruiser ‘Oleg’ was sunk outside Kronstadt Harbour, for which her commanding officer, Lieutenant Augustus Agar, was awarded the Victoria Cross and promoted to Lieutenant Commander. Seven CMBs took part in the second raid on Kronstad itself, for which two other officers were awarded VCs and Agar was awarded the Distinguished Service Order.

CMB 4 is on loan from the Imperial War Museum.

The replica of this Coastal Motor Boat, CMB 4R, was constructed in Boathouse 4, primarily by volunteers.