James Nesbitt is to star as a respectable dentist turned killer in a new TV drama about an extraordinary real-life double murder, it has been confirmed.

Nesbitt, who previously starred in BBC One's The Missing, will be crossing over to ITV for the three-part drama, The Secret.

The 50-year-old will play Colin Howell, a dentist and respected member of the local community. Howell became a murderer alongside Sunday school teacher Hazel Buchanan in 1991.

Buchanan will be played by Genevieve O'Reilly, 38, who is known for roles in Episodes, Banished and The Honourable Woman.

Howell and Buchanan met at their local Baptist Church in Coleraine, Northern Ireland and began an affair, ultimately plotting to kill both their partners, Lesley and Trevor.

The two were discovered in fume-filled car in an apparent suicide pact. It was only 19 years later that the truth was discovered, when Howell confessed to the murder and named Buchanan as his accomplice.

The drama is based on the book, Let This Be Our Secret, by Deric Henderson, the former Ireland Editor of the Press Association.

Henderson said: "It's an extraordinary story, certainly the most remarkable I've ever covered in a long career."

The Secret is written by Bafta-winning writer Stuart Urban and directed by Nick Murphy. The producer is Jonathan Curling, and the executive producer is Hat Trick Productions' Mark Redhead.

Redhead said: "This is the story of an audacious and wicked crime. It tells us something very surprising and revealing about the dark side of human nature."