Stephen Merchant and Sheridan Smith star in hard-hitting trailer for BBC factual drama Four Lives

The incidents were not classed as suspicious by Metropolitan Police until weeks after the fourth death, despite their similarity and occurrence in the same area near Port's place of residence.

Four Lives comes from writer Neil McKay and aims to tell this story from the perspective of the victims and their families, utilising "extensive research and multiple sources" to ensure as accurate an account as possible.

The first trailer below places Sheridan Smith front and centre as Sarah Sak, the mother of the late Walgate, who later wrote a book about the circumstances of her son's death. Watch below.

Stephen Merchant will portray killer Stephen Port, with the men he targeted to be played by Tim Preston (Anthony), Jakub Svec (Gabriel), Leo Flanagan (Daniel) and Paddy Rowan (Jack).

The series is directed by David Blair (BritBox's Crime) and executive produced by Jeff Pope, who has previously worked with Smith on The Moorside, which was based on the disappearance of Shannon Matthews.

Last week, an inquest jury declared that there had been "fundamental failings" in the handling of the murders, adding that the three later deaths "could probably have been prevented" had there been a more thorough and competent investigation (via BBC News).

"It is a devastating finding," said Assistant Commissioner Helen Ball. "Our thoughts are with everybody who loved these young men. We are so sorry for their loss.

"And we're also deeply sorry that there were failings in the police investigations and the responses to their murders. I give my own and the Met’s heartfelt apologies."

Four Lives will premiere on Monday 3rd January at 9pm on BBC One and BBC iPlayer. Check out more of our Drama coverage or visit our TV Guide to see what's on tonight.