> William Fairbairn, was a portly pensioner with an unusual passion: he was the world’s leading expert in silent killing

This reads like a sentence straight from a bad 70s action movie. Who had decided he was the world's leading expert? And how in the world would one know?

The "narrative history" seems to use a lot of name dropping, as witnessed by the reference to Churchill in the title. Special Operations Executive, the ministry of ecomomic warfare as well as the build up of a large air force go back to the much maligned Neville Chamberlain.