The actress says that staying still and showing no expression or emotion made the task of portraying a robot extremely challenging

Diane Morgan says the hardest thing about playing an AI-humanoid robot care-worker in new BBC comedy Ann Droid was not being able to laugh, cry or anything in between.

In the series the Motherland star - who co-wrote the six-part BBC1 comedy - plays robot assistant Linda who is bought to look after elderly widow Sue, played by The Royle Family favourite Sue Johnston.

Diane, 50, said there were times she felt like weeping at the unexpected poignancy of Sue Johnston’s scenes, which showed how lonely life can be for the elderly. “What was a hard was Sue’s got these really emotional scenes and I’m sitting next to her, motionless. But obviously I’m hearing everything, and she’s amazing. There were times, sitting on the bed, where I thought, ‘I’m gonna cry, I’m gonna cry’. And I can’t cry, I’m a robot. It was really difficult.”

The comedy star, who also plays the comedy characters Philomena Cunk and Mandy, said she had no idea the series would turn out to be touching. “We just thought it was a really funny idea but then we got Sue on board, and she gave it heart,” she explained. “I just want people to enjoy it. It leans into all those things grief and loneliness and your parents ageing and technology, all this stuff that people can relate to."

She said that initially she had no intention of playing Linda herself. “When the BBC went for it, I suddenly realised, `Oh Christ, they'll want me to play the robot’. I had absolutely no idea how to do this, but we got a movement coach who worked on Humans and he gave me the confidence."

But staying completely still to portray Linda - including not blinking - meant that Diane ended up suffering for her art. “For those dead eyes - I got an ulcer,” she said. “I wore these blue contact lenses and my eyes weren’t getting enough oxygen.”

In the story it is 2029 and Sue is on her own following the death of her husband Dave two years earlier. At 42, her son Michael (Paul Ready) feels guilty about finally moving out and so buys her a reconditioned robot carer Ann Droid Z58/100.

Diane got the idea for the series after hearing about the robots being introduced in Japan. “I read a piece which said that they’d started rolling out robots for the elderly and I thought - ‘that’ll be me’. Because I don’t have kids. I’ll be fed soup by a robot.”

She thinks it won’t be long before the AI carers become a reality. “I’m sure they are imminent. They have ones that can turn on the washing machine, make the bed. It’ll only be a few years before they can do everything. I’d get one to do the ironing, I hate ironing. And making the bed. Anything slightly strenuous - but I wouldn’t want one brushing my teeth. It’s a step too far.”

Sue said she jumped at the chance of the role in the BBC comedy series. “It was a joy of a shoot, the script was so lovely. It made me laugh - and I’m at the age where you do think about falling over. Not a lot, but it does cross your mind.”

In the storyline Sue and Linda become very close over the six episodes, much to Michael’s dismay, as he feels pushed out. “They are very, very affectionate. I don’t know if that’s because I love Diane,” Sue laughed. If she was to have a robot herself, the actress, 82, would get one to drive her around when she is no longer able to. “I dread not being able to drive any more,” she admitted, revealing that her Royle Family co-star Ricky Tomlinson has been told to stop at the age of 87.

“I can’t bear the thought. I’ve driven since I was 17 and I love it. So maybe a robot would make me feel happier, it would almost be like I was in charge of the car.”

Diane also said that a scene she wrote in which Linda performs the Heimlich manoeuvre has potentially saved not one but two lives after she was trained for the scene by a first-aider - and one of them was Strictly Come Dancing judge Shirley Ballas.

Afterwards the show’s make-up artist Jane Green, who’d been watching, was able to perform the move on Shirley when she choked on a fish bone during what the dancer called a "terrifying" incident.

And one of the show’s electricians also jumped into action when a fellow sparky was unable to breathe. “They went out for dinner that night and he saw his friend was choking,” Diane said. “Because he’d seen the Heimlich manoeuvre he did it and the food shot out of his mouth.” She added: “It’s amazing, it’s like a safety video.”

• Ann Droid starts on BBC1 on Friday at 9.30pm