Phase two begins with chief instructor Billy determined to understand his celebrity recruits inside out. With psychological insight from Dr Gareth and a rare glimpse into Billy's own past, the recruits quickly learn what's expected of them. They're thrown into a life-or-death combat scenario as they're forced to decide in a heartbeat whether to fire or hold their nerve. Then a terrifying 230-metre crawl through mud-filled tunnels pushes fears to breaking point. A brutal beasting follows - and one recruit hands back their armband.