Afghanistan, January 2007.
It's a piece of military daring that went down in history: Three Royal Marines and a Royal Engineer hold on to the side of Apache attack helicopters, heading into battle to recover a fallen comrade.
Those involved in a gripping, almost unbelievable day, tell their story, many speaking for the first time.
It begins with British forces, tasked with bringing security to Helmand Province in the South of Afghanistan.
But Lieutenant Colonel Rob Magowan commanding the IX Battlegroup has a problem.
Jugroom Fort.
The Taliban command and control centre is a crucial route for enemy fighters making their way in from Pakistan. They train there. They rearm there. Jugroom Fort is the launchpad for attacks on British troops.
But a bold plan to occupy the ancient stronghold with the battle-hardened Royal Marines of Zulu Company is about to meet intense resistance.
And amid a gruelling firefight, a man is left behind.
The Fort is told solely by current and former members of the Armed Forces.
Produced by Kev Core