A little-discussed topic and one that needed a definitive examination, this is a very interesting and well-presented volume. The author has wide and enviable access to Boulton Paul archives, both photo and document, and has made excellent use of them. The main coverage is, of course, of the Defiant, but the Blackburn Roc is briefly described also, as is the American Black Widow (an almost exact replica of an earlier British BP aborted design) and similar aircraft, but most fascinating to this reviewer are the various designs that never came to fruition.
The principal criticism I have is that the author seemingly still accepts much of the wartime propaganda claims of highly inflated "kills" and MOI blurb, long since demonstrated to be largely inaccurate. There is no need for any book published in the 21st-century to repeat such obviously unrealistic claims as, to take just one example, that Defiants shot down 21 Ju87 Stukas in a single day over Dunkirk, when the true (and far, far smaller figures) have been well documentated from official Luftwaffe returns for decades. Also the flat statement that the Blackburn Roc never operated from a carrier deck is also total nonsense as, apart from trials at sea, several were embarked for a brief period during the Norwegian Campaign, and Petty Officer (A) W. J. Heard flew one from the carrier "Ark Royal" on combat patrol off Norway in April/May 1940.
Such points apart, the book is, generally, very well done and is recommended.