Caroline Catz is a honey, an intense one maybe – the cliche would be ‘thinking man’s crumpet’ – but there’s more to her than that, as her role in Carol Churchill’s revived feminist play Top Girls proves. So don’t be fooled by her pragmatic character Louisa in Doc Martin, there’s fire in her belly, as Katherine MacAlister finds out.

Confident, serious, prepared, smart, beautiful and conscientious – these are just some of the words I’d use to describe Caroline Catz, Doc Martin’s favourite headteacher.

Over 1.9 million of you tuned into watch the last Cornish episode. But while we sit on the edge of our seats waiting to find out if Doc Martin will return, Caroline is already immersed in something totally different, without so much as a backward glance.

Because Top Girls is not a ‘plug-the-gap’ play. Written by staunch feminist Caryl Churchill in the 80s and staged by Max Stafford-Clark, it has become an iconic reflection of today’s feminist struggles, and is still utterly apt, hence its revival.

Which is why Caroline jumped at the chance to star in it: “I have always wanted to play in Top Girls ever since I first read it, and there is never a right time to be going off on tour when you have children so it needs to be something really exciting and a brilliant role... But this wasn’t a difficult decision because it’s a wonderful play with some fabulous scenes.

“And it’s so exciting to be working with Max and Out-Of-Joint again. I did Shopping and ****ing with him in ‘97 and it’s really nice to be working with him again.”

Caroline plays Marlene in Top Girls, the dinner party hostess who invites her female role models for supper.

“As all the different guests unfold, so does Marlene’s world,” Caroline explains, “and you begin to realise how she has become this businesswoman and what it has cost her, as well as how brutal and cutthroat it was in the 80s, and the compromises she made. So it’s a great play with some interesting questions.”

So does Caroline think it’s still appropriate today? “I don’t think Top Girls has aged at all. Male and female roles are still an issue, there is still no equality between our domestic and working lives, and there are still gender and economic concerns for women.

“It may be set in the 80s and therefore seen through a slight historical perspective but it was a call for change and a comment on the current financial climate, Thatcherism and individualism, financial gain versus commitment in society as well as success, apart from women as home beings, and these are the questions asked in the play. So it is very involved.”

No kidding. So not very Doc Martin then?

Caroline smiles, humouring me and ignores my question. “But that’s why Caryl wrote it to get under the skin, that’s what drove her and Max, because it’s a collaboration, so I feel in safe hands and with the current financial climate and government there is nothing dated about it.”

And what of the play’s parallels with her own life as a working mother? “Well being an actor is always a juggle. But you can’t do it otherwise. And I am always mindful of how a job will affect everyone else and whether we can all manage it, but that’s probably the same with any freelance job. Put it this way, I’m very lucky to have such a supportive family and husband.

“TV and stage work present different challenges but they both take you away from home. But then I’m doing this because this is what I love to do, plus we have to work to survive financially so we make it work.”

Even so the summers are spent filming Doc Martin in Cornwall which can’t be a bad gig?

“It has a great cast and fabulous script,” Caroline, 41, says proudly “and you never know what’s going to happen next which is nice. Plus I get to work with Martin Clunes.”

Yes, but is it fun? “We all love being there and the kids come with me for the summer and Easter holidays and have a lovely time so they are obviously desperate for me to go back for another series. We also have crowds of people watching when we film now who come from all over the world, which is great practice for the theatre.

“So it’s nice things coming in at the moment. And I feel I have a good balance between the two, but this time, although I really wanted to do some theatre, I was waiting for the right thing.”

So how is it? “It’s a completely different discipline, using a whole different set of muscles. And while filming is more bitty, tiring, weather dependent and less continuous, it’s also spontaneous. But I can only think about Top Girls at the moment because it’s very imminent.” Scared? “No, luckily I don’t get stage fright.” Clever, focused and cool as a cucumber. No wonder Doc Martin is smitten.

* Top Girls runs at Oxford Playhouse from Tuesday to Saturday.

Call 01865 305305 or see oxfordplayhouse.com Caroline is pictured, inset left, with Martin Clues in Doc Martin. Inset right, Top Girls