PREVIEW: 24 Hours In Police Custody (Ep3)

The UK's biggest, most successful true crime documentary series features unprecedented access behind the scenes of police investigations into major crimes.

DCI Adam Gallop of the Major Crime Unit in Cambridgeshire has a problem. He is in charge of the force's most mystifying and complex murder inquiry. He believes that a man who disappeared in September 2015 has been brutally murdered but, so far, he hasn't recovered the victim's body; which means he can't be sure what has happened to him and who might have killed him.

DS Mark Devine, who has investigated more than 200 murders, worries that, on the longest running job that he has tackled, he is running out of people to talk to and that any forensic evidence is disappearing. New intelligence suggests that the man may have been driven to a woodland at gunpoint by an organised crime group; and once there was forced to dig his own grave before being shot dead.

The police investigation takes officers from an urgent excavation in the woods across Europe in search of clues. DCI Gallop confesses that the search for the body is getting to him: 'I've always hated hide and seek... He's there somewhere, I just hope one day we will find him.' Cameras follow every twist of the hunt for the body; a hunt that has become a personal mission for the officers involved.

Then suddenly the case takes an extraordinarily dramatic turn - a new post appears on a Facebook page associated with the man.

24 Hours In Police Custody airs Mondays at 9pm on Channel 4.