During WW2 and for some time after the war, the Royal Air Force operated a sizeable fleet of small craft, mostly rescue launches used for recovering
the crews of downed aircraft, as well as other types such as seaplane tenders and target towing launches. Airfix's kit represents one of the best known of these, the British Power
Boats (BPB) Type 2 high-speed launch, known as the "Whaleback" from the distinctive shape of the deck and cabin.
The "Whaleback", which first entered service in mid 1940, had a hull constructed from wooden (mahogany) planks in a similar fashion to the MTBs and many other RAF craft. It was powered by three Napier Sea Lion engines (a modified version of the Lion aircraft engine) giving it a maximum speed of around 36 knots.
Most RAF launches during WW2 had defensive armament (during the early war years, especially when operating over the Channel, the Luftwaffe were a frequent threat), usually Vickers .303 machineguns in aircraft-style Plexiglass turrets. This was often supplemented by additional MG mountings and even 20mm Oerlikon guns.
Airfix's kit was first released in 1979 (as of 2009, it's still in production), the last of their 1/72 boat series before the 2006 RNLI lifeboat, and is generally similar in parts breakdown and level of detail to their other 1/72 small craft (Vosper MTB, S-10 Schnellboot) produced at the same time. Unlike these, the hull isn't split at the waterline, which makes for additional work if you're building a waterline model, but does make the hull much easier to assemble. The kit includes optional parts to build either an early-war boat (with a striking black + yellow paint scheme) or a late-war one with additional armament (including an Oerlikon gun) and protective splinter padding. The decal sheet has hull numbers for 3 different boats. 4 crew figures are also included, 3 of which are gunners.
The overall level of detail is extremely good, with plenty of surface detail moulded onto the deck and superstructure, and small parts like fittings and armament are well detailed. Some parts like handwheels and railings are slightly chunky and overscale, and (at least with more recent issues of the kit) the parts are often poorly moulded, with flash/mould seams and in some cases noticeably misaligned mould halves. Recent issues are also usually moulded in a rather soft, flimsy plastic which makes masts and flag staffs fragile and hard to rig properly; I'd recommend replacing these with brass wire.
However, as with the rest of Airfix's 1/72 range, the RAF Rescue Launch will build a very good model with only a minimum of additional work.