In Wanderlust it is Collette’s character who attempts to gee up marital sex. Picture: YouTube.com

London - Our screens are awash with middle-aged sex. And after watching first Keeley Hawes then Toni Collette in the panting throes of sexual ecstasy - in TV dramas Bodyguard and Wanderlust - I’m rather regretting my sheltered life.

At 42 and 45 respectively, these hugely talented actresses play women so desperately hot to trot that they embark on wildly passionate affairs with no thought of the consequences. Which part, at least, is true to life.

People in the throes of passion will always take risks. Yet I remained unconvinced. Do older women really want to rip their clothes off at the clink of a handcuff? Is the average middle-aged woman really obsessed by sex, sex, sex? Sorry, I don’t buy it.

It’s no surprise that Bodyguard and Wanderlust are both written by men. For there’s no doubt men and women have a very different "take" on the importance of sex.

For example, last year the brilliant Irish writer Bernard MacLaverty published Midwinter Break, a much-praised and very moving novel about a retired couple taking a weekend in Amsterdam. They are very different characters; their marriage is troubled; they suffer all the aches and pains of age - along with its melancholy.

Yet the novelist asks us to believe they have sex two or three times in one weekend. It simply doesn’t ring true - neither emotionally nor physically. I couldn’t suspend my disbelief. Even the finest writing can’t make up for masculine wishful thinking.

In Wanderlust it is Collette’s character who attempts to gee up marital sex. But there’s something innately unconvincing about the male fantasy that wifey will sidle up in transparent baby-doll pyjamas and beg to "resuscitate our flat-lining sex life".

Oh, come on! In real life she’d be more likely to bed down with the latest thriller and a mug of camomile tea.

The trouble with our society’s obsession with sexual performance is that it makes people feel bad about their own lives. That they are somehow missing out. Someone out there is always at it - so the fact that we are content to snuggle up and snore means our marriage is in trouble.

Sex experts, therapists and advice columnists keep telling us sex is essential in a healthy, long relationship. But is it really?

Millions of older couples treasure their friendship, shared jokes, companionship and are no longer particularly bothered about sex.

Why make them feel there’s something wrong with them?

Of course Wanderlust seems to be posing the perfectly serious question of whether desire can be sustained within a long, monogamous relationship.

It suggests that the act of love will inevitably become tedious when you’ve been together for years. The premise seems to be that it’s natural for both men and women to want more. We shall have to see how this drama about wandering eyes and bodies pans out. But this obsession with sex makes me worried. In my experience it usually ends in tears.

Thirteen years of writing an advice column have led me to the (unsurprising) generalisation that men want sex but women want affection.

I am certainly not saying that older women never want sex. Of course not. But in all these years I have only ever had one letter from a woman in her 50s desperate for sex - and hurt and angry that her husband was not.

Compare that with the countless problem letters I receive from women who are sad and lonely because their husbands never talk to them or show affection. There’s no comparison between the two needs.