The first twelve 40-foot Coastal Motor Boats (CMBs) were ordered by the Admiralty from J I Thornycroft's in January 1916, and by August were delivered. They were armed with one 18-inch torpedo and Lewis guns, and could make well over 30 knots. CMB 4 was one of this batch. CMB 4 had a most distinguished career. Initially she was based at Dunkirk, operating as part of the Dover Patrol, and taking part in raids on Ostend and Zeebrugge, including the famous Zeebrugge Raid of 23rd April, 1918. In 1919 CMB 4, commanded by Lieutenant Augustus Agar, was used on Secret Service operations in the Baltic. In June Agar and CMB 4 sank the Bolshevik cruiser 'Oleg'. Agar was awarded the VC. In August Agar and CMB 4, with other CMBs participated in Operation RK, the famous attack on Kronstadt Harbour. Two VCs were awarded and Agar received the DSO. CMB 4 was exhibited at the Motor Boat Exhibition at Olympia in 1920 and subsequently at the IWM/Crystal Palace.
CMB 4 is listed in the National Historic Ships Committee's Core Collection of Historic Vessels. Placed on Historic Ships Committee Register under Certificate No 400.
motor boat, constructed of wood; L (hull) 40ft (44ft including torpedo rails); W 8.5ft.