In the Vietnamese jungle, the group are tasked with a 200-foot abseil into a dark bat-infested cave. In a bustling market, the recruits must take down an armed gunman in a crowd of civilians. And then they take on each other in a game of murderball.

The last six recruits face deep interrogation and a day of sickeners, including `drownproofing' - simulated drowning. Only the physically and mentally elite will make it through.

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?

The recruits take part in extreme hand-to-hand combat. A breach of camp discipline leads to a 'beasting'. And a recruit gets stranded up a huge waterfall.

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 recruits are stalked across the Scottish Highlands by a military-trained hunter force, before facing extreme interrogation on limited sleep and rations. Who will crack?

Twenty recruits prepare to enter `Jungle Hell', the toughest phase of SAS selection. First they are tasked with traversing the 'trainasium', suspended 50 feet above the ground. Then they must complete a 200-foot abseil headlong into a waterfall.

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 recruits must master their emotions under extreme pressure - from a scary backwards dive at night to an illusion jump. There is a further shock as the mole in their midst is revealed.

The recruits are pushed to control their aggression, as they're trained with guns and take part in hand-to-hand combat, in an episode exploring loss, loyalty and self-control.

The recruits' grit is tested as Jay's undercover status is revealed and he launches a brutal beasting to expose the weakest in the group.

The recruits take on the intense close-combat murderball and surf immersion - a notorious water beasting that simulates water torture.

The recruits work in pairs as they tackle the threat of chemical warfare and execute a fast-paced extraction in near-freezing water. Then, it's time for brutal hand-to-hand combat.

Led by Ant Middleton, 25 men and women - including an ex-SAS operator working as a mole - face the latest intense course, beginning with a swim to a remote Scottish island.

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 recruits face a forward abseil and an arduous beasting by the DS. There's also an extreme water immersion exercise and a team event in a dark network of disused tunnels.

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.

21 new recruits embark upon a recreation of the brutal SAS selection process, starting with an ambush, a hijack and a 100-foot abseil, which proves to be the toughest course to date.

The remaining recruits face the final stages which consist of an interrogation and a brutal sickener. They must prove that they have both the mental and physical strength to complete the process.

The recruits are on the run across the punishing landscape, pursued by a military-trained hunter force, in a real life game of cat and mouse where only the strongest will make it through.

The seven remaining recruits are ambushed by a hunter force team behind enemy lines. Handed over to interrogators for questioning, the recruits must endure psychological and physical punishments designed to break their will and force a confession.

In the series finale, the last recruits are subjected to all kinds of punishing interrogation techniques. In the most feared phase of the course, they receive severe punishments, being buried alive, and thrown in water tanks, to force a confession.

The recruits pair up for a 50-foot freefall off a cliff. They also face a brutal beasting in the desert, which pushes some recruits to the edge, and are forced to make a split-second decision about whether to fire in a combat situation.

The recruits try a seven-metre backwards dive and face an elimination sickener on a major sand dune. After hand-to-hand combat in murderball, they're ambushed while driving back.