From the start, the recruits face a series of extreme, high-pressure tasks, including jumping from a moving helicopter into a lake and crawling across a vast canyon on a tightrope

The recruits must abseil 200 feet off a dam and climb a mountain in blistering heat with 40lbs on their backs

The recruits race each other across sand dunes in the Sahara and must cross a valley at night while avoiding hunter teams who are tracking them with dogs

The recruits must dive 10 metres into a reservoir - backwards, and blindfolded. And then they're captured and intensely interrogated in an extreme test of mental resilience, trust and moral judgement.

Eighteen recruits down, seven to go... and it's the most demanding final phase the instructors have ever designed. Some recruits have to give up, others are culled. Will any of them pass the course?