Vanessa Feltz: The delectable, desirable dish of the day is mutton dressed as lamb. Tasty!

Why should older women resign themselves to decades of frumpishness?

(Getty Images)

May abundant blessings pour upon the ebulliently tinted, vivaciously bleached head of darling, daring Joanna Lumley. She is out and proud – a mutton dressed as lamb evangelist. Not content to nip to Topshop, showcase her impressive pins in short shorts and flick her flowing tresses over her saucily peekaboo shoulder at the age of 65, the goddess of the Gurkhas has carved out a new and noble role as a MDAL cheerleader, waving her perky pom-poms in the air to inspire other ladies of a certain vintage do likewise. She's encouraging us to unleash our post-menopausal vamp, flutter a pensionable false eyelash, sew on an entirely gratuitous sequin, channel Dame Shirley Bassey and make damn sure we don't succumb without a bout of fisticuffs to the inevitable slide towards invisibility.

She's braver than you think. We 40-plus British females are supposed to know our place, and it certainly isn't in the spotlight, muffin-tops akimbo, bursting from a boob tube, bingo wings waving merrily in the breeze. Good taste decrees that once our breeding days are over, we don't do anything so vulgar as draw attention to ourselves. The advent of the hot flush is our cue to relinquish any further foray into femme-fataledom. We're meant to retire gracefully from the fray. Any flaunting of cleavage or flashing of thigh is deemed not only unwise but downright desperate. Good Lord, carry on that way and we might all end up at 10 Downing Street in sprayed-on scarlet catsuits doing a Nancy dell'Olio!

It is ordained that we must bid farewell to high fashion, flirtatious fascinators, ingeniously cantilevered balconette bras in smokey grey satin, leather trousers, bottom-hugging jeans and ostrich feather trimmed frou-frou and hello to sensible shoes, Jaeger blazers and expensively subdued "kindly ignore desiccated little old me" classics in discreet tones of taupe, charcoal and navy.

The message is clear. You are mutton. You have dared to let lubricious lusty lovely youth pass you by. Here is your punishment for passing your prime. Henceforth and for ever you must dress as mutton. Every morning as you button your inoffensive blouse and swathe your puckered knees in a frumpy "forgiving" skirt, you must acknowledge that you are sexually defunct. Every evening as you zip up your bog-standard, collar-detail-distracts-from-ballooning-waistline, not so little black dress you are forced to embrace the demise of your desirability.

The rules are inscribed in stone. If you have a facelift, for God's sake, make it subtle. Don't dust off your wrinkled décolletage, even at Christmas or the funerals of those you loathed. Have the courtesy to shield strangers from your drooping dugs. Chop off your hair, even if it's still shiny and lustrous, because there's no one more pathetically deluded than a 1664 – a woman with cascading pre-Raphaelite tresses who looks 16 from behind but turns round to reveal the raddled visage of a 64-year-old crone. Don't go near high fashion. Navajo earrings and Aztec knits will be desecrated by your spare tyres and liver spots. Uncover no more than a well-turned calf, and that only if absolutely necessary. On the beach, shelter behind aviator shades, sarong, parasol and a Kindle. If you are fat, wear a kaftan that matches the wallpaper and expect to drive yourself home.

Joanna Lumley's bold rallying cry will be an elixir to British women at their most vulnerable. Boy, do we need balm for our battered confidence. If you question British repugnance at the mere suggestion of a woman who has seen better days, pause, if you please to ponder the seismic impact of Helen Mirren's red bikini.

Readers of Paris Match wouldn't have batted an eyelid. They're bombarded with snaps of Catherine Deneuve, Jane Birkin and Isabelle Adjani flexing their seasoned torsos on Cap d'Antibes sun loungers and worship the trio as the apotheosis of female deliquescence. The Italians, who are congenitally incapable of diving into a bowl of spaghetti alle vongole without raising a glass to the mature charms of Sophia Loren, wouldn't have given two hoots about Dame H in her cossie. But those pictures punctured a fundamental tenet of British culture, that older women are, at best, for laughing at, at worst, for running from.

Think Yootha Joyce as Mildred begging in a lather of frustration for the favours of ghastly George. Think Les Dawson's harridan of a mother-in-law. Think huge, horny Hattie Jacques bearing down on reluctant Kenneth Williams. The punchline is crude and simple. Birds on the turn are mad for it but – here's the hilarious bit – no one wants to give it to them. Boom boom!

Enter Dame Helen, stage left. Great Scot! If Dame Helen was so obviously a free bus pass piece of tottie, might the unthinkable be true? Could there possibly, living happily in cul-de-sacs, avenues and tower blocks the length and breadth of the country, be women who'd never see 45 again who were fancied and fanciable, thoroughly enjoying the hurly-burly of the chaise longue?

Just in case you're thinking the elephant in the article is me, let me assure you that I haven't failed to notice that Lumley and Mirren are paragons of female pulchritude. Most women, even at their most nubile, can look plug ugly on occasion. I have variously been called "the woman who ate her audience" and "an ancient All Saint". So what? You don't have to be a slice of slim size six mutton to enjoy decking yourself out like a spring lamb.

The sheer joy of being MDAL isn't reserved for the trim, toned, Botoxed or pretty. Any Mutton Chops with the verve to bother deserves the right to don fishnet tights and stilettos, wiggle into something flimsy from Whistles and strut her funky stuff. There's no fatwah on fat, no qualifying audience with Anna Wintour, no cut-off point after which it's mandatory to appear in orthopaedic shoes and comfy cardie.

Rock on Joanna, Carol "Make mine Mouret" Vorderman, all the louche lascivious Loose Women, Esther "My Louboutins are shinier than yours" Rantzen, Cilla "Have you seen my legs lately?" Black, all the Bananarama "They're no ladies" ladies, Kelly "Cougar extraordinaire" Hoppen, Maureen "Oy! Am I soignée!" Lipman, Moira "Sultry" Stewart, Arlene "More flexible than a 14-year-old" Phillips, miraculous Lulu, Baroness Susan "Mini-mini" Greenfield, Jo "Husband? What husband?" Wood and the unsung monstrous regiment of women who are gleefully adding to the gaiety of nations and relishing every faux fur-trimmed, fauve-printed, death-defying second.