While SOE agents Marjorie Stewart and Richard Heron depart by train, Gubbins enlists Gus March-Phillips to assemble a ground team to destroy the Italian supply ship Duchessa d'Aosta and two tugboats attached to it.

Using the neutral Swedish fishing trawler Maid of Honor, Gus and his allies, Graham Hayes, Freddy Alvarez, and Danish naval officer Anders Lassen (the only non-Commonwealth subject to be awarded the Victoria Cross), begin the slow sail to Fernando Po.

Upon discovering that SOE saboteur Geoffrey Appleyard, whom Gubbins had sent ahead on the assumption that Gus would show interest in wanting him on the team, was captured by Gestapo agents, they divert course to a Nazi-controlled section of La Palma for a rescue mission.

Upon learning that the Duchessa intends to depart three days ahead of schedule, Gus has his crew sail through a British naval blockade of Nazi-occupied West Africa despite knowing they will be arrested should their unauthorised mission be discovered.

While waiting to be court-martialled, they are saved and recruited by Churchill as part of his 'Ministry of Ungentlemanly Warfare', as their actions have not only severely damaged the Nazis' naval strength, but also have allowed the United States, which recently entered the war following the Japanese attack on Pearl Harbor, to join the European theatre.

[5] Paramount Pictures acquired the rights to Damien Lewis's book, The Ministry of Ungentlemanly Warfare: How Churchill's Secret Warriors Set Europe Ablaze and Gave Birth to Modern Black Ops,[6] in 2015.

The website's consensus reads: "Cranking up a true story of derring-do into a high-octane action flick that's heavy on spectacle if not suspense, The Ministry of Ungentlemanly Warfare is another solid entry into Guy Ritchie's pantheon.