David Tennant has undergone a chilling transformation for his latest role.
Nilsen, also Scottish, was a serial killer who is said to have confessed to killing 15 men in London between the years of 1978 and 1983.
Watkins will play mass murderer biographer Brian Masters in the series that’s been written by Luke Neal.
“This starts with Nilsen’s arrest and is looking at him through the eyes of the police officer trying to identify those he killed and deliver justice,” ITV head of drama Polly Hill said.
Nilsen targeted gay and homeless men and would make his victims drunk before killing them.
It was later revealed he would keep their bodies for long periods of time before attempting to flush their body parts down the drain.
His crimes were discovered after a resident in his apartment block summoned a plumber to investigate why the drains were blocked.
Des will air on ITV in 2020.