Celebrities undertake a series of extreme tasks, including jumping backwards out of a helicopter and hand to hand combat, as they begin the challenge of completing the gruelling SAS selection course.

Recruits are pushed to tackle their fears head on in a 60m high forward abseil, while a brutal game of murderball on a black mud plain leaves one recruit with a near concussion.

In an abandoned abattoir, recruits face a life or death decision before they are drilled physically into the early hours of the morning. Will they bow out from exhaustion or find the true grit needed?

In freezing waters with plummeting body temperatures, recruits wait to be rescued by their teammates before they face a test of pure grunt and teamwork. An emotional departure surprises the group.

In a punishing day, recruits crawl across a jagged ravine on a single rope above the ocean; are submerged in crashing, cold surf; and face a physical drilling that leaves them on the brink of collapse.

The fatigued recruits drop from a helicopter into 4-degree water carrying 20kg backpacks, before making their way to shore as a group then racing to the top of a mountain.

Recruits are brutally awoken by the sound of gunfire and a botched rescue attempt unfolds. Messages from home test the recruits' emotional resolve while a relentless pack march takes its toll.

In a dangerous backward fall, the life of the jumper is in the hands of a fellow recruit. During an honesty test, some gobsmacking truths are shared. And a simple mistake results in a serious injury.

Recruits race up a snow-covered mountain dragging a 60kg sled. Exhausted, they must then swim under ice, battling hypothermic conditions, only to discover the weakest will be sent home.

In a daunting challenge, recruits are tasked with rescuing a downed pilot. As bombs explode and guns fire, they must make the right decision amidst the mayhem. After a brutal combat course, an explosion on base has an unexpected outcome.

Recruits are chased overland in near freezing temperatures. Once captured, they face intense interrogation before they attempt the final phase of the course, a series of brutal physical tasks called The Sickener, designed to push them over the edge. Who will prove worthy of passing SAS selection?