From the back cover:

Built in large numbers in the years leading up to World War 2, Bristol's Blenheim saw use as both a fighter and bomber thanks to its high speed in relation to the biplane types it was then replacing. Aside from its work as the staple medium RAF bomber from 1939 through to 1942, Belnheims also served as pioneer radar-equipped nightfighters in 1940/41 and long-range patrol aircraft with Coastal Command. Obsolete in Europe by the end of 1940, the Belnheim continued to serve as a frontline bomber in North Africa, the Mediterranean and the Far East well into 1943.