This is what a 40-plus woman really looks like. And it's not pretty.

A couple of seasons ago I was watching a reality TV cooking program that probably rhymed with Fry Bitchen Mules and was blithely referring to couple of mature aged housewives as ‘The Old Birds’ when my husband pointed out a harsh truth.

“You know they’re your age, don’t you?”

“Rubbish,” I thought as I Googled furiously, scrolling through the contestant bios to prove him wrong.

And it turned out he was wrong. The women were not my age at all. One was actually a full five years younger than me. Which made me – in my own words – an Old Bird.

That’s the funny thing about ageing. Even as the years creep by and the wrinkles etch themselves into deeper ravines around your eyes and your smiles lines sag into jowls,  you still think “I look pretty good”.

In your mind’s eye you are a glamorous 25-year-old – or maybe 30 at a pinch.

What it’s like to be an attractive woman [via the ladies of Reddit]. Post continues after video…

This complete blindness to the way you look to other people means when you are sitting in the parent teacher interview across from a hip 27-year-old art teacher you are thinking ‘this woman and I could hang out together – we could even have a squad – if only she if she didn’t hate my daughter so much’.

And later, when you are  having a similar conversation with an older teacher, you politely call her Mrs because you think she is your mum’s age, until your daughter informs you she is also two years younger.

Most of the time we are very bad at judging how we look. We even start to get confused about what others look like. Sometimes I see young people and can’t tell if they are 18 or 28. And it’s not because my vision is going. It’s because you just lose track. How old is Helen Mirren anyway? 50? 80? Something.

Certainly whenever I see a 40-plus actress I give her photos a very thorough scan, to see if I can recognise myself and can compare how I am “holding up”.

And the result is usually not favourable. Airbrushing and lots of makeup at movie premieres work wonders. And then there are the genetic freaks like Elle Macpherson. Pictures of her diving from a yacht in the Mediterranean last year still give me sleepless nights. How could anyone that age look THAT good? And after all those years in the sun? And the smoking. And the parties!

But this week actress Cameron Diaz finally offered a reality check on the business of being 40 plus when she posted a  no makeup selfie to Instagram to promote her new publication, The Longevity Book.

I’m so excited to continue the conversation because learning that you can age well, will actually help you age better. If you understand how your body works then you can take action to help keep it in the best possible condition so it can carry you through a long and beautiful life. | Read my full post at www.OurBodyBook.com @thebodybook #linkinprofile #longevitybook #knowledgeispower #everyoneages

A photo posted by Cameron Diaz (@camerondiaz) on Mar 30, 2016 at 9:17am PDT

And while no makeup selfies are really 2015, this one was pretty cool, because Diaz – who is clearly a very beautiful woman –  looked every inch her 43 years. Great bones etc, etc. But not young. Not glowing. Kind of tired. A bit faded. And definitely wrinkly.

But it’s kind of rubbish. As much as we rail against it, we all know  a beautiful 20-year-old woman will turn heads – men’s and women’s – quicker than a well-preserved 50-year-old.

Hello Ladies! Happy Fall! Hope everyone is enjoying this glorious time of year; the chillier air, the changing and falling leaves; all of the markers of another year coming to a close, and a hint at the new one about to unfold. I first wanted to thank all of you who answered our call this past summer to send in any questions you might have about aging in a female body. I am so grateful for your participation, as it allowed us to address your inquries in the next volume of the @TheBodyBook. It is centered around the mental, physical and emotional journey of aging. And as we diligently put the finishing touches on the book, we’d like to ask for your help once more. This book is for you and about you and that’s why we’d like to see you on the cover. Much like the cover of the Body Book, under the jacket, were we featured women of all different shapes, sizes, builds and ethnicities. We would like for you to feel represented again, this time to show where you are in your process of aging. So we invite you to take a picture of yourself. It should look much like the one I have here; against a plain background, this general framing-you can crop closer to a portrait, and the higher-def the better! We’d like to see more of that beautiful face of yours than the body this time. And if you want to snap one with yourself and your mom and your daughter together, or any multiple generations or expressions of your journey with aging, we’d love to see those, too! And for the 50 we use on the actual cover, we’ll send you a signed copy of the book when it hits bookstores in April. So be yourself with it, be brave with it, have fun with it, and we can’t wait to see. Thank you again and Happy Selfie-ing!! Ox, Cameron To submit, click the link in my profile. A photo posted by Cameron Diaz (@camerondiaz) on Nov 6, 2015 at 2:01pm PST

Love, hopefully. A family who loves you. A decent wardrobe, A great job. And smarts.

So thanks Cameron. You might have posted that picture because you wanted to promote your book. But your selfie was nice all the same. It was honest and it made me relieved. Because I thought: “This is what I look like”.  Not as good looking maybe, but definitely that age.