Fans have been given a first look at Sheridan Smith in character as Sarah Sak, the mother to serial killer Stephen Port’s first victim.
Smith stars in The Barking Murders, a factual BBC One drama told from the point of view of Port’s victims and their families.
The serial killer drugged and raped young men before dumping their bodies near his home in Barking, east London.
Anthony Walgate, a 23-year-old aspiring fashion designer from Hull, was his first victim.
Stan & Ollie actor Rufus Jones, Stephanie Hyam from Bodyguard and Leanne Best from Line Of Duty have also been announced as appearing in the series.
Samuel Barnett, from BBC America’s Dirk Gently’s Holistic Detective Agency, and Robert Emms, who shared the screen with Smith in Cleaning Up, complete the casting.
They join Stephen Merchant, who plays Port, and Jaime Winstone, who will appear as Donna Taylor – one of the sisters of victim Jack Taylor.
The three-part factual drama is written by Jeff Pope and Neil McKay, who were responsible for The Moorside and Appropriate Adult.
Pope said: “Neil McKay 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.”
Executive producer for the BBC Lucy Richer said: “I’m so pleased that we’ve assembled such an extraordinary cast to be a part of bringing this important true story to screen with sensitivity and compassion.
“This compelling story shows the tireless courage and determination of the victims’ families and friends to find out what really happened; it’s an honour to tell it on BBC One.”