Growing up is, in large part, the process of discovering other families do things differently from your own. So startling is the divergence that you can barely credit the evidence before your eyes. They hate each another. They are only allowed to watch TV on Saturdays. They don't talk at mealtimes. Their mum puts lace doilies under her cakes. But by far the most shocking discovery I made was that some people's parents slept in separate beds or - horror of horrors - separate bedrooms. "Why?" I asked a school friend whose father had his own quarters in a large Sevenoaks townhouse. "I don't know," she said, as it slowly dawned on her that other people's parents occasionally slept together.
My mother and father slept in the same bed until the day my father died of cancer, at home. When my older siblings and I were small we often piled in too. I remember my mother telling me that she always held my father's hand until she fell asleep, and this image bolstered the intense faith I had in their union. To everyone else they looked like an irascible, pensioner publican with an inexplicably young bride knee-deep in nappies, but I knew they clasped hands unseen. The whole point of being together, so it seemed to me, was sleeping together - this was at an age where I understood and cared very little about sex. My grandparents shared a bed, my aunt and uncle shared a bed, my gay uncle and his love shared a bed. A couple of those beloved relatives snored with the ferocity of wild boar on the rut. "That's what ear-plugs are for," said my granny.
But the shared marital bed is an institution under attack. A survey by the National Association of Home Builders in the United States has predicted that, by 2015, 60 per cent of custom-built homes will have two master bedrooms. The trend is expected to cross the Atlantic. Once upon a time intimacy and sex were the prizes marriage brought you; now you can be sexually intimate within seconds of surfing the net. Once people were physically exhausted at the end of the day's labours; now we're always tired, but never properly fatigued. We have children later in life and the shock of sleep disruption is greater. You only need to add one thing - a snore, a fart, a grunt - to the powder keg and KER-BOOM! Exit one spouse to the sofa's sanctuary.
Three Pelling siblings are currently sleeping apart from their spouses. My older brother works a night shift (top excuse); my sister's husband is an insomniac and, when he does drop off, his legs jerk fitfully. He's sleeping in the spare room until they can afford a new, extra-wide bed. And here I must also, reluctantly, stick my hand up. Although it's against my creed (by which I mean the western romantic tradition - do you think Jane Eyre slept apart from Mr Rochester?) I have recently taken to sleeping in my office. It started by accident and seemed inconsequential, as many hairline fractures do. I envisaged a once-a-week escape, so I could make an early start to write this column. Crucially, it enabled me to perform my "slumber" routine with the alarm: it rings, you push a button for a 10-minute cat-nap before it rings again, before I press the button to "slumber" again, before it rings again etc etc. A routine that reduces my husband to a, hyperventilating, pillow-over-head zombie.
But what I discovered via this harmless marital exeat was disquieting. The spare bed didn't leave my back aching, the duvet was warmer and I no longer had to sleep by an open window as Siberian winds blasted my face. Nor was I trapped by the wall, as my husband insists on taking the accessible side of the bed, leaving me to clench my bladder or crawl over him and the cat.
I escaped my little boy's nocturnal snufflings, his 3am sobs: "I want Thomas/digger/ dinosaur/milk/kitten," "Not that one!" "Daddy do it!" "Waa!". A performance swiftly followed by my husband bellowing, "I can't take any more." But the best thing about my weekly exile was being able to read in bed for the first time in 14 years. This forced the realisation that my husband and I view the whole notion of bed in diametrically opposed ways. For him it's a no-frills sleeping machine. For me it is (or should be) a plush platform for life's richest pleasures: toast, tea, chocolate, novels, Radio 4, champagne, negligées, sex, jokes, Grazia and my son clambering in for a chat (after 7am). I feel that a life conducted from a feathery backdrop of plump pillows - akin to Evelyn Waugh's Mrs Stitch - would not be lived in vain. I'd be happy to receive visitors; they could join me under the counterpane. No gossip is more delightful than that conducted over a duvet. All of which is anathema to my husband.
And yet, and yet, and yet. Despite my time in boudoir Shangri-la (extended by the old sore-back routine) I sense it's dangerous to linger too long, lest I never find my way back. There's a symbolic potency in the shared bed, the spooning, the hand clasped and the mumbled "I love you" before talking ceases. You never see separate bedrooms in Hello! On some level - however unjust - we judge the success of a marriage on a basic ability to share its most intimate and disputed terrain. I suppose it's a sign of a couple's willingness to compromise.
Speaking of which, I am returning to the marital bed, but my husband must suffer the "stultifying" indignity of a luxurious new bed. As the man at Savoir beds (suppliers to the Savoy) says, "it's a mystery why people spend so much on sofas and so little on beds. They aren't furniture, they're theatres of the horizontal."