HMS Ocean is Britain's biggest warship and the flagship of the Royal Navy. She's a floating village with her own hospital, shop, police force, church, bank, laundry, gym and even pubs. But this village is also an amphibious assault weapon, designed to sail across world and, when necessary, bring violence to an enemy. Its crew have a deep affection for their ship. But one third of these men and women are new recruits, off to sea for the first time. And the 20-year-old vessel is showing signs of strain. Keeping it going requires non-stop maintenance. With exclusive access to the ship and her crew, this series follows HMS Ocean on a sensitive seven-month active deployment, culminating in becoming the first ever UK ship to lead a US task force in the Middle East, policing some of the most volatile waters on the planet and co-ordinating the fight against Isis.