A new true-crime drama on ITV is set to explore the chilling case of serial killer Dennis Nilsen.Dennis, which will air on the channel over three consecutive nights from Monday (September 14), will depict the police investigation into Nilsen's murders.It is based on material from the book Killing For Company by Brian Masters and the story will be told through the prism of three men – Nilsen played by David Tennant, Detective Chief Inspector Peter Jay played by Daniel Mays and biographer Brian