Costal Motor Boat

The original batch of Coastal Motor Boats (CMB’s) were designed and constructed in 1916 by John I Thornycroft at Platt’s Ayot at Molesey 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 an 18-inch Whitehead torpedo.

Boats of this type were used in raids on Zeebrugge and Oostende but, most famously, in 1919 on the White Russian fleet in the port of Kronstadt.  On this daring raid, the cruiser “Oleg” was sunk for which Commander Augustus Agar and the boat involved (CMB 4) were awarded the Victoria Cross.

“Coastal Motor Boat” was a “camouflage” term for the boat, so as to not give away its true purpose.

Our boat is intended to be a fully operational replica of CMB 4.  The construction of the boat
is a project funded by the Chancellor using LIBOR funds.

Boat Stats

Length Overall



8ft 6in




4 tons




Double skin mahogany

Date Built

Currently under construction

Boat Yard

Boathouse 4, Portsmouth Historic Dockyard


Supported by:

Supported by Regional Growth Fund