Channel 4 Monday 4 September 9pm

You could actually hear the floors hitting one another – boom, boom, boom – and I thought to myself 'oh shit, this is it, we didn't make it.' Fire-fighter Sal D'Agostino

'I was going to be dead in a few seconds, and I remember feeling, I hope... I hope this is fast.' Fire-fighter Mickey Kross

It was the most incredible story of 9/11; how 12 fire-fighters, a police officer and an office worker survived inside the North Tower of the World Trade Center as it collapsed on top of them. In this film the survivors describe hearing the floors above them giving way, one after another. Convinced that they were about to die they shared what they assumed were their last thoughts. They then endured burial under half a million tons of debris but were able to contact the outside world when all hope seemed lost. Eventually they emerged into the post-apocalyptic landscape of Ground Zero, the only survivors to walk out of the wreckage.