In the dark waters of the Atlantic, the German U-Boat fleet was taking a monstrous toll on Allied merchant shipping, to the extent that Admiral Jellicoe feared Britain would cease to exist as a fighting force unless something was done to stop the U-boat menace.
Spurred on by the sinking of the Lusitania in May 1915 the Royal Navy introduced a new weapon to fight against German submarines - the decoy boat or Q Ship as they were known.
In a game of cat and mouse, merchant shipping losses began to fall thanks to the ingenuity of the Q Ship fleet. We hear about so-called "panic parties" held onboard merchant ships, why sailors wore women's clothes whilst on deck, the reason why the Royal Navy commandeered a lorry full of dead parrots, and how a three-legged dead dog and a rolling pin combined to hoodwink the commander of a German submarine.
We also look at one of the great controversies of WW1, the Baralong incident in 1915, and hear the story of a heroic Naval officer whose clandestine activities lead him to become known as The Mystery VC.