You look amazing. How do you feel?

On my uproarious 40th birthday party I felt, well, 20. Now I'm in my sixties I feel around 50. I still feel quite toned. I swim a lot and, as a choreographer, I'm dancing all the time in rehearsals. Apart from Strictly, I'm involved in the new ITV drama Britannia High and London musicals Flashdance and The Sound of Music. At times I think: “When are you actually going to grow up, Arlene?”

How do you do it all?

I don't know. Getting up at 6 this morning wasn't easy, but I've always been blessed with a high-octane personality, which I've probably inherited from my dad. Even in his eighties he'd walk from his home in Belsize Park, northwest London, to the East End. Plus, I'm fired up by loving what I do. I'm never bored.

You must be hugely organised

I'm a list-maker par excellence. I carry around not one, but two notebooks full of lists and my computer contains the precisely ordered details of my entire life. Sadly, the hard drive crashed last year and everything, including my photos, was destroyed. I can't tell you what I went through physically and emotionally. I'm only just getting over it.

With your job, staying in shape must be a breeze

When I'm at my optimum weight, 8st 7lb, I feel terrific. But at my current weight, 9st 8lb, I don't feel good at all. I started sliding last Christmas when I decided to add roast potatoes to my lunch. Unheard of. Since then I haven't been able to turn my back on pasta, bread, cheese, buns. I keep telling myself: “Tomorrow is the day when I start eating fruit vegetables and lean organic meat again!” But tomorrow never seems to come.

Anything else you'd change about your body?

I'm 5ft 3in. Even another two inches would be a dream. I could do with a facelift, but wouldn't have one. I'm phobic about needles and knives and wouldn't want to risk a general anaesthetic. I want to be around to see my grandchildren. But I recently discovered the non-surgical facelift and have treatments at a salon two or three times a week. It uses ultrasound to lift and tighten everything with amazing results.

Did having a baby (her second daughter Abi at 47) keep you feeling young?

It definitely did. I was determined not to look like the oldest mum at the school gate. A lot of people felt I was being really selfish. They said: “What if you don't live to see her grow up?” My answer is that none of us ever knows what's around the corner. My mum had me in her twenties but died of leukaemia when she was only 43.

Are you more aware of your own mortality?

Yes, my sister and I have a constant feeling that we are living on borrowed time and have done so since our forties. Losing my mum has made me all the more determined to live to see my daughters grow up.

Ever discussed it with a therapist?

Yes, I had a few sessions when my daughter Alana, 28, was little. I was a single mum trying to do my best, but I mistrusted my own judgment. It helped me to believe that, in the end, I was the best judge of how to raise my child. But I hated it. Therapy, like yoga, just seems to involve too much sitting around.

Does religion give you any comfort?

I was raised in a strict Jewish family in Manchester, although I'm not particularly religious. What I still carry with me is the unshakeable belief that family is at the core of existence. But I've rejected the guilt that seems to be associated with every leading religion.

Being with a man 11 years younger must help to keep a spring in your step

Yes. I still want to be attractive to Angus; sex and intimacy are hugely important.

You've been together for 20 years. Any tips?

It works for us because we are respectful of each other. For me, my daughters are in pole position, then comes my career and then it's Angus. He has never had a problem with that.

Did you suffer from working mother guilt?

Oh yes, guilt with a capital G. You're always feeling, “I should be there, I'm not doing enough! I must be a terrible mother.” I'm incredibly close to my daughters and they don't seem to be showing any signs of damage. Would it have been better if I'd been a stay-at-home mum? We'll never know. But if you asked me which role had given me the greatest fulfilment, I'd have to say that it was being a mother. It stands above everything else. No question.

Can you ever be too old for sequins?

I don't think so. We're not obsessed with youth on Strictly Come Dancing. Len Goodman and I are both in our sixties and Bruce Forsyth is 80, for heaven's sake.

Britannia High, ITV1, from late October

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