Walker, R.N. is punchy first-round WW2 history, focusing on Captain Frederic John "Johnny" Walker, the most decorated and successful anti-submarine warfare commander of the Second World War. The book glides over his early life and pre-war career as a successful misfit in the Royal Navy, a natural leader who clashed with his superiors and who's career seemed to have stalled when war broke out.

The Battle of the Atlantic was one of the critical points of the war. Without convoys from the Americas, Britain would have starved, Russia would not have received important lend-lease aid, and the Normandy landings might never have occurred. This was a campaign without fronts or decisive moments, a grinding war of attrition between escorts and U-boats.

In this war, Walker made a name for himself as an aggressive and preternaturally gifted hunter. In command of the Second Support Group, consisting of a core of Black Swan-class sloops, Walker sought out U-boats wherever they were most active, either in the Bay of Biscay or attacking allied convoys. He pioneered several tactics, specializing in a directed quiet kill, where he would stand off maintaining Asdic (the British term for Sonar) contact, while directing another ship to creep in and nail the target with depth charges. The descriptions of combat are plenty exciting, if a little repetitive, while the rest of the book is standard hagiography.