James Norton has revealed the mental effect of playing his notorious Happy Valley role, saying “it goes into your subconscious and somehow it emerges in your dreams”.

The 37-year-old actor portrays villain Tommy Lee Royce in the BBC One drama, which is set to return for a third and final series on New Year’s Day.

Speaking at a Happy Valley regional screening event in Halifax earlier this month, Norton said: “I’ve been filming horror movies, and with this too you have to find authenticity but it can cost you.

“You have to keep the other part of you sane. I got rid of Tommy and have a feeling of losing the family and friends you make on the show.

“I do remember from the first series, I had really violent scenes. It was written and filmed much darker, and I would spend ages beating her up.

“It goes into your subconscious and somehow it emerges in your dreams.”

The series, created and written by Sally Wainwright, follows Sergeant Catherine Cawood – played by Sarah Lancashire – on the trail of murderer and sex offender Tommy Lee Royce.

The new six-episode series will see Catherine discover the remains of a gangland murder victim in a drained reservoir, sparking a chain of events leading back to her former nemesis and the father of her grandson Ryan, played by Rhys Connah.

Happy Valley screening
James Norton and Rhys Connah (Danny Lawson/PA)

Ahead of the series airing, Norton also discussed what it is like to be associated with such a violent and dark character.

“Tommy and me are slightly different, I think!” he said.

“Happy Valley was a great moment for my character, because I could prove to producers that I was ready to transform. I owe it everything.

“But I’ve had my fair share of roles since which are nasty guy with a heart!

“But it’s wonderful to be associated with the show – we know the affection for it.”

He added: “For people to come up to you and say Happy Valley, it means the world.”

Happy Valley
James Norton as Tommy Lee Royce in the third and final season of Happy Valley (Matt Squire/BBC)

During the event, Norton spoke about his favourite location to film in, saying: “Prison. Sarah [Lancashire] has a massive responsibility with lines and the mental acrobatics.

“I basically just walk down corridors a lot and pose with long floppy hair. I enjoy that, because I don’t need to do very much and look cool!”

He also revealed that he wore nothing under his prison jumpsuit during filming in order to play his part as accurately as possible.

He said: “I asked them if they would let me take the boiler suit from this series home. The reason they wear these fluorescent colours, is so they can be seen but also they wear nothing underneath.

“It was the same here because I wanted to be authentic, but it was so cold!”

Happy Valley airs on BBC One at 9pm on New Year’s Day.