A new BBC series goes behind the scenes of the gruelling training that Royal Marine Commandos have to go through, culminating with four tests that must be passed. Watch a clip here: 

Commando: Britain’s Ocean Warriors lets viewers see first-hand just what it takes to make the grade for one of the world’s most revered military units, while also exploring the ‘heritage, ethos, culture and indeed the modern role’ of the Royal Marine Commando.