If you like to defy the passing of the years by refusing to 'act or dress your age' you may be part of a new generation: Amortals. Author Catherine Mayer's reveals the 'ageless' pros and cons of the approach in her new book Amortality, with a quiz to see if you fit the mould.

By Gabrielle Fagan.

Celebrities have long practised the art of defying the years - think Helen Mirren, 65, posing in that red bikini, Madonna still lithe at 52, and Demi Moore, 48, who looks more like an older sister than a mother when with her 16-year-old daughter, Tallulah Belle.

But, it seems, more and more ordinary mortals are no longer content to recognise the age boundaries traditionally dictated by society and are gleefully flouting the stereotype about the way they should look or behave.

That doesn't mean they're all rushing to the gym or the cosmetic surgeon - although a small proportion will - but more significant are those whose attitudes remain resolutely 'young'.

They're the people who take adventurous 'gap' years or pick up new careers at an age when they would formerly have been expected to retire, dress the way they want rather than the way they should, and are generally refusing to be defined by a date on a birth certificate.

"I call them amortals," says Catherine Mayer, author of new book, Amortality: The Pleasures And Perils Of Living Agelessly.

"They are people who are challenging some of the prejudices and structures associated with all the phases of life, and especially in their middle and later years.

"While the word, amortality, may not be familiar - yet - you're bound to recognise the symptoms in yourself or others.

"Perhaps people say, 'You don't act your age', maybe you're not even sure how someone your age should act, or you know someone who's still surprising everyone by enjoying sports or hobbies way beyond the expected age 'sell-by' date."

They are, however, certainly not the norm. A report by Kent University for the Government has found that Britons believe old age starts at 59, nine years earlier than in other European countries. Greeks regard old age as 68, while in France 63 is considered old.

The notion that we're old in our late fifties must be challenged according to Minister for Pensions Steve Webb.

He argues that attitudes have not kept pace with medical science and rising life expectancy. He estimates that 11 million people alive today will live to 100 years old.

"We need to challenge our perceptions of what 'old age' actually means. It is no longer a time when people are sitting back and enjoying the twilight of their lives, instead it is often a time for new choices and new opportunities," he says.

Mayer agrees and points out that across the developed world the average lifetime has lengthened by 30 years since the beginning of the 20th century.

"By comparison with previous generations who saw death on a daily basis - a parent killed by war, plague or pre-antibiotics and scientific developments, incurable illnesses - nowadays many of us may not even experience someone dying until we're in middle age," she says.

"So people don't structure their lives around the inevitability of decline and death, instead they prefer to ignore it."

Mayer, 50, who describes herself as an amortal, says: "I'm still hyperactive, still compelled to accept dares and push myself to sample new experiences, however daunting. I enjoy deep sea diving with my father, 81, another amortal.

"I believe society is gradually re-writing the rules of what it means to be 40, 50, 60 or beyond. As author Mark Twain once said, 'Age is mind over matter. If you don't mind, it doesn't matter'."

Although, she acknowledges, there are perils as well as pleasures in amortality.

"Embracing old age isn't a bad thing, if that means appreciating your accrued wisdom and feeling comfortable in our loosening skins," she says.

"Amortals are often in denial about ageing and death and may become depressed and angry when confronted with reality."

And non-amortals may mock what they regard as the 'antics' of those whom they perceive as 'getting down with the kids' by wearing similar clothes or sharing music tastes.

Their scorn may be misguided, she points out, and refers to a recent BBC One programme, The Young Ones, where celebrities aged in their seventies and eighties were asked to 'go back in time'.

They had to live, dress and think as though they were only in their forties in a house decorated and equipped as if it were 1975.

Within weeks researchers found their mental faculties and physical health improved drastically.

"Dignity is overrated. If you're the kind of person given to muttering, 'Act your age, not your shoe size' - beware!

"Conforming to outdated, restrictive ideas about ageing is just as damaging," says Mayer.

"The moral of the story is that it's healthier to be mutton dressed as lamb than mutton dressed as mutton."

Quiz: Are you amortal?

Answer the following questions - tick the answer that most closely matches your immediate response.

1: The difference between the age you are and the age you feel is: a) More than 10 years; b) Up to 10 years; c) I feel the age I am; d) No idea. Age is an irrelevance.

2: Describe your typical Sunday: a) I often have to catch up on work but I also find time for friends; b) I usually have a lazy day and watch TV; c) Church, household chores and family pursuits; d) Hard to say, but as busy as the rest of the week.

3: The late thirties and forties are the best ages to have babies: a) I agree, and I/my friends have done just that/are planning to do that; b) I'm not sure that's true. It's probably better to have kids when you have more energy; c) I disagree. It's unfair on the kids who have older parents; d) I haven't got round to thinking about babies.

4: Your friend's new lover is 25 years younger than your friend. You: a) Don't think the age difference matters. They're soul mates; b) Understand the attraction but the age gap means the relationship is unlikely to last; c) Think 'there's no fool like an old fool'; d) Hadn't noticed.

5: You are permanently stressed and worried. You turn to: a) Therapy. I start by fixing myself; b) Retail therapy. It always makes me feel better; c) Prayer. It always makes me feel better; d) Stress? The only thing that makes me stressed is having nothing to do.

6: Your ideal holiday would be: a) Action-packed. An adventure; b) A mixture of relaxation and sight-seeing; c) I like to spend quiet time at home; d) I prefer work trips. They're a better way to get under the skin of a country.

7: Your fitness routine involves: a) Guilt. I belong to a gym but rarely go; b) I exercise/play a sport but I'm not as fit as I used to be; c) At school/college I played a vigorous sport; d) I don't really need to exercise because I am always running to the next appointment.

8: When you think about retirement you: a) Shudder. I never want to stop working; b) Wonder if I'll ever be able to retire; c) I'm looking forward to my golden years; d) I haven't really thought that far ahead yet.

9: The following statement best describes your attitude towards getting old: a) I don't intend to get old the way people used to; b) It comes to us all, I suppose; c) I look forward to the dignity and wisdom of age; d) I haven't really thought that far ahead yet.

10: Every life ends in death. Discuss: a) Maybe, but science is on the point of finding ways to make us live longer; b) That's true but I'd really rather not think about it; c) And death is the beginning of eternal life; d) I haven't really thought that far ahead yet.

Answers: Mostly As: Bona fide amortal: You have strong amortal inclinations and are already living agelessly, at least in some respects.

Mostly Bs: On the way to amortality: You have latent amortal tendencies that may well develop in the future.

Mostly Cs: Mortal soul: You have significant immunity to amortality and are unimpressed by many of its manifestations.

Mostly Ds: Amortal to the max: You're so detached from external concepts of age that you probably don't even realise how agelessly you live.

:: Information: Amortality: The Pleasures And Perils Of Living Agelessly, published by Vermilion, priced £12.99. Available now.

Tried & tested Conventional yoga may have you tied up in knots, but a new technique promises to be different. Sarah O'Meara tests a movement and meditation class which promises to stretch and tone without strain.

What is it?

Angada Yoga combines meditation techniques with movement and unlike most other forms of yoga is personalised to the individual.

Brought to the UK by Vinay Menon, Chelsea Football Club's wellness guru, he aims to rebalance his customers by de-stressing their minds and bodies.

What's it like?

At the beginning of the hour-long session with the creator of Angada, Vinay Menon, it's clearly stated the session is tailored to you.

Menon assesses physical wellness first by taking your pulse and explaining the principles of his yoga method, which are about finding 'inner balance'.

"This is not a yoga where you aim to lose so many pounds in as many weeks," he says.

"I'll be taking you through a form of rehabilitation, using your breathing to help you."

Breathing is central to the session. We start with an exercise that has me bending over and breathing out for 20 counts.

Then Menon begins moving me into yoga positions, encouraging me to stretch further into poses with every exhalation - and the sensation is euphoric.

With my eyes shut, letting Menon guide my body with his voice and hands, I become entirely lost in the process.

While the stretches are no less strenuous than in traditional yoga, the difference is I'm 'willing', rather than straining my muscles to respond.

As I breathe and move around the room I recognise basic yoga moves, yet have no idea what to expect next.

Menon tailors the poses and programme specifically for each client.

Surprisingly, I find Menon's close presence soothing rather than distracting or embarrassing. As my eyes are almost always closed, his presence isn't intrusive and I find it aids concentration and helps me focus better on his flow of instructions.

Angada Yoga is intended to heal the body and five sessions are recommended for full benefit, but after one I felt distinctly calmer and uplifted.

:: Information: Personal appointments with Vinay Menon at The Chelsea Club's Antara Spa start from £90 for an introductory session (special offer price until November 1: normal price £150). A course of five sessions is recommended. For information call 0871 223 1224 or visit www.thechelseaclub.com