Daniel Mays – the actor who played DCI Peter Jay in the true-crime series – revealed he has experienced nightmares about the Scottish serial killer.
“When you’re preparing for a role like this, you have to delve into what happened and it was really, really tough,” he told NME.
“I woke my wife up screaming because I was having a nightmare that I was in an attic with Dennis Nilsen.”
However, Mays also added struggling with the show’s dark story helped him better understand his character.
“The content was really toying with my mind, but that was a great thing to experience because when you look at it and policing at that time and what Peter and his team went through, they weren’t privy to any form of counselling or anything like that,” he said.
“Their counselling was going down the pub and drinking copious amounts of alcohol, not opening up to their wives. Talking about your feelings wasn’t common for men of the 1980s, so the drama is also an amazing investigation into what it was like to police at that time too.”
Mays also revealed that David Tennant’s performance as the titular serial killer also heightened the realism on set.
“Sitting across from David during an initial interrogation scene when he looked so uncannily like Dennis was just eerie. I found it as close to what they must have been experiencing at the time and that felt pretty tricky,” he said.
“David completely embodies the role. He very much kept himself distant from all the actors because of the difficult subject matter – you could tell that he was really in character and he wanted his space. It’s an amazing performance.”
Mays’ character, DCI Jay, retired from the police two years after the investigation into Nilsen closed. He died in 2017, aged 79.
As his son Simon recently revealed, his father never felt he received achieved justice for Nilsen’s victims.
Speaking about how Nilsen was only prosecuted for only six victims, he told HertsLive: “The problem with the case is that Nilsen always claims he killed 15 or 16 people. I think they only found six bodies and the police at the time shut the whole case down without Dad wanting it to be shut down.
“It was always a bit of a tainted case for him even though everyone looks at it as this big, positive case that they found this killer. For Dad it was always that we never got to finish it properly.”
The Real ‘Des’: The Dennis Nilsen Story is on ITV on Friday 17th September at 9pm . You can buy Brian Masters’ original biography on Dennis Nilsen, Killing for Company, on Amazon. Find out what else to watch with our TV Guide.