Kate Humble and JJ Chalmers are given unprecedented access to the Royal Navy. Cameras on board a British warship follow the hunt for a Russian submarine. Kate gets special clearance to go behind the scenes at Britain's secretive submarine base at Faslane in Scotland. JJ reveals what it takes to be an elite Royal Marine Commando as he journeys back to the beginning of his military career.

Kate Humble enters the secret and clandestine world of submarines. She is invited to step on board a British nuclear powered attack submarine at the secretive base of Faslane in Scotland. Former Royal Marine JJ Chalmers heads back to his old stomping ground, the Royal Marine Commando Training Centre in Devon where his training began 18 years ago.

Kate Humble joins British Warship HMS Dragon and the crew of over 200 off the coast of Norway as the ship prepares for its next big mission. She witnesses them testing their weapons to confirm that the ship and crew are ready for battle. JJ Chalmers is invited to join the Royal Marines Band Service for a very special performance at Manchester's Bridgewater Hall.

JJ Chalmers heads to the unforgiving terrain of Dartmoor to push himself to the limit to find out whether he still has what it takes to match the standards of a Royal Marine. Kate Humble is granted behind-the-scenes access aboard HMS Iron Duke - a frontline British warship with 200 crew on a mission to safeguard the nation's shores.

JJ Chalmers learns how a warship performs one of its most dangerous and difficult manoeuvres, refuelling at sea. He joins a massive 39,000-ton tanker, operated by the Royal Fleet Auxiliary, as it conducts the dangerous operation just 40 metres apart from a moving warship out on the high seas. Kate Humble takes on the extreme Submarine Escape, Rescue, Abandonment & Survival course.

Kate Humble is granted rare access aboard the British warship HMS Dragon, and when a ferocious storm hits, she sees how a warship and her crew battle towering seas to stay safe. Dwayne Fields is recruited to take a flight in a Royal Navy helicopter, but first, he must complete the same life-saving training required of every crew member. Also, JJ Chalmers revisits the Falklands Conflict.

JJ Chalmers heads to HMS Raleigh in Cornwall, the home of Royal Navy training, to see how recruits are prepared for the harsh realities of war. Kate Humble is aboard a warship as a brand-new helicopter pilot takes an important step in their career - landing on the deck of a moving warship at sea for the very first time. Also, JJ explores the legacy of HMS Ark Royal, one of the Navy's most iconic aircraft carriers.