After three back-to-back challenges, the 13 remaining recruits are battered and bruised, sleep-deprived and physically exhausted. But they are about to face their toughest challenge yet, all under the orders of Jason Falla, a former member of the Australian SAS. For the first time, the recruits will learn what it is like to go behind enemy lines as they take part in a military role play to help supply a guerrilla force. Under Jason's eagle eyes, they will have to prove that they have the mental strength to operate in hostile territory whilst marching through the night and facing the demands of the guerrilla army. Who will be the first to break?

• Kelechi Okafor
• Reggie Yates