I can't help wondering if it matters whether sex was something we had a burning desire to do in the first place or not. Surely, the point is that we both enjoyed it in the end? Picture: Steve Lawrence

Shona Sibary

There’s something nobody tells you before you get married – a closely-guarded secret known only to those women who have already spent years in wedlock.

The secret is this: that a night will come, some time into married life, when you will lie next to your husband, hardly daring to breathe, and think: “If I don’t move for a moment or two, please, please, let him think I’m asleep.”

In the early throes of passion, it hardly seems possible that there will come a time when you will actually dress to get into bed – and yearn to stay that way. But so it is.

Every night I carefully don my “armour” – pyjama bottoms, socks and a long-sleeved top. Then I stand in the bathroom and brush my teeth for as long as I can, in the hope that my husband, Keith, will fall asleep before I make my unenthusiastic appearance in the bedroom.

It wasn’t always like this. When we first met, 19 years ago, sex was spontaneous – and something we both wanted on a regular basis. It didn’t matter whether it was pre-dawn or the middle of the afternoon – we were riding on a wave of endorphins, our desire for each other instant and strong.

But the only thing that’s instant and strong in our house these days is the coffee.

If Keith dared to wake me for a middle-of-the-night liaison, then he’d probably get a rather grumpy response.

It’s not that we can’t find time for love-making. There are, after all, 24 hours in the day. It’s just that, for some reason, none of those hours is sex o’clock any more.

Sex columnist Rowan Pelling recently wrote about a woman planning to marry a man who was adamant she sign a prenuptial agreement.

It wasn’t, as you might think, that he was worried about his future finances. He wanted her to commit to a contract stipulating how often they would have sex in their married life.

In short, he was demanding she promise to love, honour and copulate at least twice a week, until death do them part.

This seemed to get everybody in a terrible lather. Schedule sex? Like a dental appointment? Or a Pilates class? Women were united in collective horror.

Men, of course, thought it an inspired initiative, though as one male acquaintance pointed out: “I’m always on a promise – it’s just that my wife has never been very good at keeping it.”

All of which got me thinking. If scheduling something motivates me to do tasks I would otherwise never get round to – aerobics sessions, for example, or spring cleaning – then why not schedule sex?

After all, with four children and busy lives, being spontaneous about anything at all is a ludicrous notion for me and my husband.

I suggest this scheduling idea to Keith, assuming he’ll be delighted. Instead, he looks suspicious. “What do you want in return?” he asks, patting his trouser pocket to check his credit card is still there.

Poor man. Just a decade ago, I was pouncing on him, lustily, at every opportunity. So how could we have reached a point where, when I propose sex, he assumes it’s because I’m opening negotiations for a new dress?

Something needs to be done, so I open the family diary and peruse our options.

“How about Monday and Friday nights?” I suggest.

“Not Fridays,” Keith replies. “What about Monday night and Saturday night?”

“Can’t do Saturdays,” I counter. “The girls always have someone here for a sleepover.”

“What about Monday night and Saturday afternoon? We can plonk the kids in front of a film downstairs.”

Keith looks at me as if I’ve gone mad. “It’s the rugby! There’s a match every Saturday. Why can’t you move your book club on a Tuesday night?”

I point out that, if we’re sticking with Mondays, we will have had sex the night before. Shouldn’t we stagger our trysts? In the end, we agree on Mondays and Thursdays, then sink onto the sofa, exhausted by our negotiations.

Comfortingly, it seems Keith and I are not alone in our predicament – since the latest research shows that the older we get, the less love we make.

According to the most recent Sexual Wellbeing Survey, the average person has sex 127 times a year, and the average married person has sex 98 times a year.

Statistics from The Kinsey Sex Institute reveal that the average 18 to 29-year-old has sex 142 times a year; 30 to 39-year-olds, 86 times a year; 40 to 49-year-olds, 69 times a year; and the over-50s have sex 52 times a year.

Crucially, however, the survey also showed that those who agreed to have sex for their spouse’s benefit often reported that they actually began to feel turned on and achieved an orgasm. They also felt far happier afterwards for having sex.

So, when Monday comes around, I try to take a positive view. As I’m dressing in the morning, I even give my underwear a second thought and decide to wear a G-string instead of my habitual big panties.

My husband and I both work from home. After the children have gone to school, Keith is ensconced upstairs in his office and I’m in my usual spot —Macbook on lap in front of the TV.

Suddenly it occurs to me that this is our opportunity. Why try fitting sex into an evening schedule when we have a quiet house to ourselves in the day?

Anyway, if we have sex now, I don’t have to wear this uncomfortable G-string for the rest of the day.

I pop my head around the door of Keith’s office to propose my new plan, but he’s in the middle of a conference call and gesticulates at me to go away.

So I do what any self-respecting woman would do under the circumstances, and remove all my clothes before visiting him again – naked.

Keith’s face is a picture. However, my husband – always a stickler for a timetable – will not deviate from what has been put in his diary.

And there I was thinking romance was dead. That night, we climb into bed and face each other warily. Neither of us feels remotely in the mood but then we never feel remotely in the mood, which is why – potentially – this idea of a fixed routine might work.

If we both commit to kick-starting our libidos, there may be some hope. I think the term is “fake it til you make it” – a sentiment which feels particularly pertinent tonight.

Afterwards, I’m pleased we did it. Keith mumbles something about “doing it more often” before rolling over and snoring.

I can’t help wondering if it matters whether sex was something we had a burning desire to do in the first place or not. Surely, the point is that we both enjoyed it in the end?

Experts agree. While some critics see scheduling sex as the death of spontaneity, others see it as a positive component of a healthy relationship.

Dr Eli Coleman, professor of human sexuality at the University of Minnesota Medical School in America, says that prioritising sex can revitalise a romance after the initial excitement has worn off.

Indeed, a recent poll of 1 000 US adults found that 45 percent reported planning trysts with partners in advance.

However, Coleman cautions that couples shouldn’t feel obliged to follow through if they’re not in the mood. “Psychologically it is not erotic to feel pressured,” she says. “It’s not erotic to go through the motions when your mind and heart really aren’t there.”

Which brings us nicely to Thursday night. It had been the evening from hell. The children were fractious from a week at school, our toddler was teething and I had a work deadline looming. The thought of compulsory sex – when all I wanted was to sit in a hot bath with a glass of wine and a book – made me feel mutinous.

“Come on then. I suppose we’d better get on with it,” I said, climbing into bed, grumpily.

“Wow, you’re hard to resist,” was Keith’s stinging riposte.

Instead of having sex, we talked about how little we both felt like making love.

We reminisced about the days when it was easy to feel turned on, and Keith reminded me how, on our honeymoon, we had made love three times a day.

And then something miraculous happened. The mood suddenly changed, and we went from: “No way!” to “Wey hey!” in a matter of minutes.

Before we knew it, we were having sex for the second time in seven days.

Week number two of scheduling sex began with an altercation at breakfast about me leaving the car key in the ignition overnight – again.

The row rumbled on throughout the day, so by nightfall I’d rather have bedded down with any other man on the planet than my husband.

In an attempt to stall the inevitable, I pottered round the bedroom picking up socks and bits of fluff from the carpet.

“Shall we do it tomorrow night instead?” Keith suggested. “Turn the light off when you’ve finished procrastinating.”

The following evening, we were both in a better frame of mind, and made up for what we had missed out on the previous night.

Now, I’m happy to report, this experiment is teaching me that the more sex I have, the more I feel like having it. Keith agrees: “It sounds unromantic, but when you’ve fallen out of the habit of being intimate with each other, it can take drastic measures to put it back on track.

“I was dubious at first about fixing a set time for intimacy because it seemed so clinical, but it worked. All we needed was to make space for each other, and the rest happened naturally.”

Not that it works for everyone. Film director Guy Ritchie reportedly claimed that his eight-year marriage to Madonna disintegrated when she started planning their sex life in her diary around her sessions in the gym.

For him, this level of meticulous planning, weeks in advance, took the thrill out of it.

However it happens, though, all evidence points to the fact that an active sex life keeps couples together.

And relationship expert Denise Knowles admits she regularly advises people to set time aside for each other.

“Scheduling shows a commitment on both sides,” she says. “You don’t have to say what you’re going to do with the time you’ve set aside, but often just being together will put sex firmly back on the agenda.”

Keith and I have discovered this to be true. As long as we don’t get too hooked on the idea that sex is compulsory on Mondays and Thursdays, we have found that setting time aside to be together invariably means that intimacy will follow.

This has been a great comfort to me, since I was starting to worry that I no longer fancied my husband and he no longer fancied me. Thankfully that wasn’t the case – we’d just fallen into the trap of letting everything else take priority.

Setting sex in stone (or at least in pen) has brought us closer together. If we’ve made love the night before, the irritants which arise in the day somehow seem easier to navigate.

Knowing that future intimacy is already planned and non- negotiable has somehow given our sex life a structure it was sadly lacking.

My only dilemma now is what to write in the family diary. Just the other day, our nine-year-old quizzed me about why the letter “S” keeps appearing in it in red pen.

“It stands for sleep,” I lied quickly. – Daily Mail