The factual drama focuses on the families of the victims of serial killer and rapist Stephen Port (Stephen Merchant), and their fight to find the truth about what happened to Anthony Walgate, Gabriel Kovari, Daniel Whitworth and Jack Taylor.

Now a widely criticised police investigation, the series will shed new light on the case and tell the story from the perspective of the victims’ families including Anthony Walgate’s mother Sarah Sak (Sheridan Smith) and Jack Taylor’s sister Donna Taylor (Jaime Winstone).

The BBC also announced new cast members have joined the drama, including Rufus Jones (Stan & Ollie), Stephanie Hyam (Bodyguard), Leanne Best (Line Of Duty), Samuel Barnett (Dirk Gently's Holistic Detective Agency) and Robert Emms (Cleaning Up).

Jeff Pope commented: "Neil and I are delighted to be working with Sheridan Smith again, who brings such honesty and passion to every character she plays.”

“Stephen Merchant didn't hesitate when we asked him to play serial killer Stephen Port and we are so grateful that he has agreed to take on such a difficult and challenging role.”

"This compelling story shows the tireless courage and determination of the victims’ families and friends to find out what really happened,” added Lucy Richer, Executive Producer for the BBC.

“It’s an honour to tell it on BBC One."

The three-part drama is due to air in 2019 on BBC One.