generally referred to them by their numbers. In 1947, MGB 2009 was fitted with a Metrovick gas turbine, thereby becoming the world's first gas turbine powered naval vessel. Types British Power Boats Early-war Motor Anti-Submarine Boats (MA/SBs) built by BPB Co. were converted from early 1941 into MGBs. These included 63-feet and 70-feet types. 63-feet MGBs (numbered 40-45) were of 24t std displacement and powered by 2-shaft Rolls-Royce petrol engines developing 2,200bhp for a top speed of 40 knots. They were rearmed for the MGB role with 1 x 20mm Oerlikon aft (some may have briefly carried a Rolls gun until the Oerlikon was available), a twin HMG turret on the coach-house roof and 2-4 x .303-inch MGs (two twin mounts would be mounted abreast the wheelhouse). 70-feet MGBs were of several different original batches or types: MGB 6-21 originally had 3-shaft Napier petrol engines for 1,650bhp and a top speed of 27 knots, being later refitted with Packards for 3,600bhp and 38 kts, while MGB 46 and MGB 50-67 had 3-shaft Rolls-Royce installations for 3,300bhp and a top speed of 36.7 kts. All were of 28-30t std displacement. Individual armament varied, but most boats had 2 x twin HMG turrets abreast the bridge (some early models had the single dorsal turret seen on the 63-feet type) in the case of ex-French boats like MGB 66 these turrets relaced a pair of twin 0.303-inch turret which had been carried side-by-side amidships. Heavier gun armament on these boats, located aft, was initially either a 2-pdr 'Rolls gun' or less commonly a Boulton & Paul quad 0.303-inch MG turret. Surviving boats were later rearmed with a far more effective Oerlikon in the aft position. 71½ ft Motor Gun Boat BPB built 34 purpose-built 72-ft MGBs (also referred to as 71.5-feet). Capable of 40 knots, they carried a hydraulically-powered 2-pounder gun mount forwards for engaging other vessels, along with a twin powered 20mm mount on the aft cabin roof and two twin .303-in machine guns (one either side of the wheelhouse) for additional firepower in surface actions as well as defence from aircraft. Some early boats even carried a Holman Projector right aft. Side-dropping depth charges and smoke generators at the stern completed the loadout. Over one hundred vessels of this class built, first ones were given identities MGB 74-97 The second series were numbered MGB 107-onwards. After the initial 34 MGBs, further