A study of 3,000 women also found that most say the perfect age for a man is 30 – like Ashton Kutcher, the “toy boy” of actress Demi Moore, 45.

But 39 is the age most women felt, or expected to feel, happiest, most attractive and confident.

It is the age of X-Files pin-up Gillian Anderson, singer Cerys Matthews and Friends’ star Jennifer Aniston, whose new boyfriend, musician John Mayer, is 30.

The research was for Debenhams, whose spokeswoman Caroline Adams said: “Women look after their skin and bodies now and are more at ease with themselves in their 30s – career paths are mapped out and relationships are more stable.”

But 52 per cent of women said they dwell on how their looks will change as they age. A third believe physical beauty is more important than personality for getting on in life.

Women look after their skin and bodies now and are more at ease with themselves in their 30s.

Debenhams spokeswoman