Actress Ruth Wilson has said playing her own grandmother in an upcoming BBC drama series was “one of the hardest things I’ve done”.

The star of Luther and The Affair faced the challenge of acting in the role of her own family member, whose revealing memoir has become the subject of a BBC One drama.

New series Mrs Wilson charts the discovery of a family secret, revealed in the memoir, that Wilson’s grandmother was married to a serial bigamist.

Her mysterious husband Alec was also a novelist and a spy.

Wilson said it was “really difficult” to take on the role of her grandmother but she wanted to take the part in order to play her properly.

She said: “I’m still processing it, I think. You’re actually acting out scenes that happened.

“It’s quite an odd experience anyway, let alone being a family member, and it let me understand her in a much deeper and emotional way, I suppose.

“And during it, it was really difficult. I think it was one of the hardest things I’ve done.”

Wilson said the challenges of playing her ancestor became quite surreal. Her memoir was handed down to Wilson’s father and uncle, and their place in the story was strangely close to home.

She said: “There were just moments where I’d get a flash of ‘oh wow, this is my own family story, this is quite crazy’.

“And there were weird moments like giving birth to my dad. Really weird moments that I had to move through.”

Mrs Wilson is on BBC One on November 27 at 9pm.