She came to national recognition in the BBC’s long running sitcom about a West London family, but Claire Skinner’s latest play tackles the difficulties of caring for dementia, says Bridget Galton.

Claire Skinner’s most recent screen role ended in the grisly sight of her character’s horrendously burned body being worked on by a trauma team.

A cast of Skinner’s teeth were clenched in the mouth of her body double in Jed Mercurio’s graphically realistic medical drama Critical.

“I kind of knew where she was headed, she wasn’t going to last long, but self-immolation with the alcoholic hand-rub in the changing rooms – no-one saw it coming,” she chuckles.

“It was interesting doing the research, going into hospitals meeting surgeons and experts who taught us how to look like we knew what we were doing, then learning that medical dialogue was like studying for some weird exam - like a foreign language you have to learn almost phonetically.”

It’s a far cry from Skinner’s best known role as harassed West London mum Sue Brockman in the now sadly-ended sit-com Outnumbered.

Over five seasons, millions took the Brockmans to their hearts as the fictional children, who improvised much of their dialogue, grew into teenagers.

“We were so lucky with the writing and with those kids,” says Skinner, who only has two children herself.

“The two writers Andy (Hamilton) and Guy (Jenkin) both have three children who were always two steps ahead of our kids in development. They took the time to write very carefully and specifically about what it was like.

“Everything was tailored to the kids, it was a calm, small shoot so they would feel relaxed and free to come up with all the lovely stuff they did.”

She believes Outnumbered’s success lay in showing the warts and all reality of the demands of modern parenting.

“It’s that thing of all the fabulous children are somewhere else doing something fabulous while mine are just watching telly and hitting each other.

“People related to how deeply flawed we were. I remember an episode where a kid comes for a play date and [Sue] sneaks a look in his book bag to see what standard his handwriting is – I identified with that!

“Or the pilot where she was combing Karen’s (Ramona Marquez) hair for nits and there was a load of them in there – her poor dad was mortified.”

She adds: “It was good that it moved away from ‘kids say the funniest things’. I remember when Daniel (Roche who played son Ben) suddenly turned into this man mountain and came back with a deep voice. They wrote a lovely scene where he lifted me up.”

From one of the nation’s best-known mums, Skinner is now playing a daughter, caring for an elderly father who’s losing the plot.

The Father, by French playwright Florian Zeller, has been described as a mesmerising, powerful, and distressing drama that takes you inside the condition of dementia by showing events through the eyes of a protagonist whose perceptions keep altering.

The audience is wrong-footed and forced to question the truth as complete strangers turn up in his flat, and characters pop up in different roles so you’re never not sure if they’re sinister or caring.

“It’s told from the point of view of an unreliable narrator,” says Skinner. “You are presented with a story, but when you try to piece it together you see inaccuracies with the way he is perceiving it. It’s deliberately disorienting to show the effect of having gaps in your memory, the frightening moment when you feel the ground shifting.”

Balancing her need to care for her sometimes cruel dad with her own life and relationship tests the limits of the daughter’s patience.

“Their relationship, what it has been, what it is now and what he imagines it to be, has been chopped into little fragments and put back together differently.

“I have had to imagine what actually happened and play that, but the heart of it is the pain of watching a loved one losing themselves.”

Despite numerous screen roles, Skinner has never deserted the theatre, and loves the rehearsal period.

“I often have a real urge to go back into theatre; it pushes me further. Piecing together a character, working out the world you inhabit, how you relate to people, looking for clues in the text, having the time to experiment; I love all that, it’s like playing a huge game.”

She feels fortunate to have worked with several inspirational directors early in her career, including Mike Leigh in Life is Sweet.

“I was so lucky working with directors like Alan Ayckbourn and Trevor Nunn who were like teachers, when I was young enough to want to learn. Working with Mike was brilliant but it does spoil you a bit, you want everyone to work like that.”

A shy child, Skinner doesn’t think timidity is inconsistent with the urge to perform.

“It’s a weird one, there’s lots of us introverted actors, sometimes it’s easier to pretend to be someone else – once you are nicely immersed in character – but getting up on your feet in rehearsals can be quite painful. You feel exposed.”

Lord only knows how exposed she felt when she met her future husband director Charles Palmer when he was a focus puller behind the camera and she was doing a nude scene.

“Often they put your kit-off scenes early in the schedule, but when I walked into the room, he was so sweet and respectful. I asked him later, ‘Did you look?’ and he said, ‘Of course I did!’

Ultimately Skinner’s acting springs from a desire to communicate, “to really make people feel what your character is feeling. There’s the reaction from an audience, a connection between you and them. You are within the world of the play yet very aware of them. You never forget they are there or that it’s all for them.”

The Father runs at The Tricycle in Kilburn High Road until June 13.