This episode is about trust. The recruits are teamed up in pairs, then take a free-falling abseil into a rocky gorge and plunge into freezing water, with their partners responsible for saving them.

For the first time, female recruits join the selection process. In a dramatic opening episode, the women fall behind the men; how many will make it through to the end of the first stage?

With the conditions deteriorating, the recruits must negotiate beastings in the snow and a night out in a blizzard 3000 metres above sea level, while the DS increase the psychological pressure on them.

The remaining male and female recruits face gruelling challenges designed to test their mental and physical strength, including a 200-foot forward abseil and an infamous boxing task

The remaining recruits must cross a 200-metre gorge, swim beneath the ice on a frozen lake and navigate a perilous valley at night, while trying to avoid capture by a local hunter force and their dogs.

The remaining men and women's final challenge is also the most psychologically demanding: resistance to interrogation, as they're subjected to stress positions, white noise and relentless grilling.