And so to bed: Sales of super-king mattresses are rocketing

But they're not helping intimacy, just creating more space for the TV and children, says Peter Stanford

Our super king-size bed arrived in a last, desperate attempt to get some sleep. When there had been just the two of us, our ancient, inherited four-feet wide futon, latterly with the edge taken off its concrete stuffing by a mattress softener, had been perfect – contemporary, cosy and the antithesis of anything either of us had grown up with in the suburbs. But then along came one child, then a second, and both were determined to occupy our bed too. Plus theirs bears, books and Bob the Builder.

Letting them in was, we assured ourselves, simply a short-term fix to get them accustomed to going off to sleep without one or other of us having to spend half the night on all fours trying to crawl out of their bedrooms, without setting off the creaking board, all the time singing "Moon River". There were just too many creaking boards.

But the futon was so squashed, we felt like The Family from One End Street. The seven little Ruggles in Eve Garnett's children's classic, though, had no choice. Their tiny house wouldn't fit another bed. In ours, by contrast, there were two going begging but for either of us adults to slope off to one of them in the middle of the night felt like the first step on a slippery slope to letting the children come between us emotionally as well as physically.

It was only when both of them took to serenading sunrise by practising the moves they were learning at Tumbles Tots that we – and the futon – gave way. In its place, we ordered the biggest bed on offer at our local shop. And soon the super-king's 6ft width was the balm that restored some sanity to our nightlife. Margaret Thatcher may have thrived on four hours' sleep, but look how Mark turned out.

I recall all this now because it seems we were not alone. Figures released by John Lewis and Tesco suggest Britain is fast becoming a king-size nation. The time-honoured British double bed that, at 4ft6in wide, was plenty for our parents and grandparents is being moved out in favour of that extra 6in, side-to-side, afforded by a king-size, or the 1ft6in if you plump for a super-king. In 2008, John Lewis was selling 15 per cent more doubles than king-sizes. Last year, though, the mattresses were turned, with king-sizes outstripping doubles by 34 per cent.

Tesco, meanwhile, reported a 45 per cent growth in 2010 in sales of king-sizes and super-kings. And that trend is verified by the National Bed Federation – an association of divan manufacturers. While king-sizes have increased their market share by almost 100 per cent in the past four years, the traditional double's share has shrunk by getting on for 15 per cent.

So why is size suddenly so important in the bedroom? Changing attitudes to being a parent is certainly a part of it. I can scarcely ever recall going into my parents' bedroom, let alone being so free as to climb into their bed at night. Truby King and the childcare gurus of yore would have made them send me straight back to my own room. As, indeed, the redoubtable Gina Ford still does, but it would seem that despite so many people buying her "contented baby" books, many of us take no notice of what she says and embrace a more relaxed style to parenting that extends to letting our small children sleep with us.

Bed manufacturers have long been nudging us in this direction anyway. The National Bed Federation funds the Sleep Council and it has been busy producing chapter and verse on how you get a better night's sleep in a king-size or super-king. In a recent survey it asked 20 couples first to sleep for several weeks in a standard double, then to upgrade to a king-size. The guinea pigs reported back that in the bigger bed they woke up in the night less often, were more comfortable, got more sleep and started the day feeling more rested. Though only 15 per cent of them had considered buying a king-size before they took part in the survey, half said they were now planning to make the change.

I'm not disputing the findings – more space obviously means more room to stretch out – but it worth noting that the exodus from the old-fashioned double has not happened of its own accord. We have gently been having our collective arms twisted – not least by the very words used to describe the different widths of bed. King, super-king, emperor (7ft wide) and caesar (8ft) all chime easily with that age-old myth that our homes are our castles.

And, as more people have heard the message, economics have inevitably played their part. The price differential between the grades has dropped. Steve Bond, general manager at Big Table is selling basic doubles with mattresses from £600 and king-sizes for just short of £700.

But it's not just about price. What bed you sleep in is increasingly presented as yet another lifestyle choice. So it's not simply about accommodating sleepless infants, or getting a better night's rest so as to be bright-eyed and bushy-tailed at the office, it's about the sort of person you are.

Cue the mood music. And the commercials do make it all look very enticing, your very own luxury hotel room without leaving home. There are, for example, the ones with a king-size bed multitasking as a play area, with Boden-clad children happily occupied on wet days when the outdoor trampoline is drenched, doing gymnastics on the parental bed while mum and dad, perfectly coiffed and usually showing a bit of well-tanned flesh (rather than bags and the straps of a feeding bra) manage to snatch such a blissful 40 winks that they are smiling in their sleep. Do road test this one at home. It is a social experiment/endurance test I have yet to hear of being repeated.

And even when the kids are occupied in another room destroying the pocket springs of their own beds, the glossy lifestyle images present a king-size bed as a home entertainment hub cum sofa cum desk, all rolled into one. This is the king-size bed not as somewhere to sleep, but as a "social space".

There's a January sale advertisement currently running with a king-size that includes within its faux leather footboard a plasma screen television that pops up at the flick of a button. It always puts me in mind of those Teasmades that an earlier generation believed made their bedrooms hi-tech until they bought one from Timothy Whites and were awoken by a scolding spurt of hot water.

The "TV Bed" – the latest must-have in a roll of honour that stretches back through four-posters, sleigh beds, round beds and water beds – also boasts other optional extras such as a side rail to accommodate a DVD player, a set-top box for the full range of channels, and a games console. Even if your partner was so far away on the other side of the mattress that you had to resort to semaphore with your bed socks to attract their attention,

the chance of finding a convenient moment to interrupt them between their favourite film, CD, PlayStation game or booting up their hard drive, becomes increasingly remote.

Which brings me round to another obvious explanation for our new found penchant for bigger beds. Is it part and parcel of evolving into a society that has finally cast off its Victorian sexual inhibitions and acquired in their place a taste for divans to match unbuttoned libidos? That might be one conclusion to draw from artist Tracey Emin's notorious condom-strewn double, shortlisted for the Turner Prize in 1998, but those spoilsports at the Sleep Council damned this theory in a 2008 piece of research. It showed that 40 per cent of us rarely go to bed at the same time as our partners, a quarter of couples sleep in separate rooms on a regular basis, and eight out of 10 say they are more interested in checking their emails at night than anything more human and intimate.

So what our bigger beds are really saying about us is that we are a stressed, overworked generation rather than an oversexed one. As well as expecting to have USB ports and flat screens where the Gideons used to leave a Bible, the modern two-earner couple hankers at the end of a long day at the office, topped and tailed by the strains of commuting, not to mention the demands of children, for nothing more than a bit of space to themselves. When you are overstretched and knackered, the last thing you want is your partner's elbow in your side, or a fight for the duvet.

It may sound appallingly unromantic, but it has apparently been going on for centuries. On display in London's Victoria and Albert Museum is the Great Bed of Ware, made for a Hertfordshire inn in the 1590s and given an honourable mention by Sir Toby Belch in Twelfth Night. It is often referred to as the world's first ever king-size, and at 11ft wide – bigger than a modern caesar – guaranteed guests at the White Hart Inn a good night's rest.

Or perhaps not, because it was reputed to sleep 15 – there are plenty of names carved into its posts, though no suggestion that all were under the covers simultaneously. Eleven feet doesn't sound quite so roomy for such a crowd. Sixteenth- century hotel guests, though, would have been a good deal thinner and shorter. And that may be another motive pushing us towards the king-size. We ourselves are becoming more king-size.

Rates of obesity are increasing at an alarming rate, while average male height, currently 5ft 10in, goes up, academics calculate, by three quarters of an inch each generation as a result of changing diet. Some 30 per cent of under-25s are now over 6ft tall. And while a king-size is best known for allowing you to feel the width, it also gives an extra 3in in length. In a standard double, toes hang over the end at 6ft3in. In a king-size they are fine until 6ft6in.

It is all beginning to make such good sense that the only puzzle now seems to be why even more people aren't getting bigger beds. That may be down to two factors.

The first is the rise in the number of one-person households. A king-size might seem a bit excessive for one, though Steve Bond at Big Table does report a parallel rise in sales of what my mother used to call a three-quarter bed, but which is more properly known in its 4ft-wide glory as a prince.

The other query is whether modern bedrooms can actually accommodate a king-size. Our super-king laps up a good chunk of the main bedroom of a generously proportioned Victorian terraced house, but builders have been making ceilings lower and walls closer ever since.

A 2009 report by the Commission for the Architecture and the Built Environment found that the average British room in a contemporary new build is just 15.8 sq m, half the size of its equivalents in the US and Australia and the smallest in Europe.

That makes your average British bedroom roughly 12ft by 12ft. Bringing in a king-size is therefore, in theory, perfectly possible if you don't mind bruised shins, but may mean squeezing out the chest of drawers and wardrobe, although, in the trend towards ever smaller rooms, the traditional box room or third bedroom in your average semi is now so petite that all it is good for is as a walk-in closet.

Whatever the logistics of our craving for more space in our beds, it is definitely not entirely a new problem. My parents' generation, for example, faced it and came up with a typically less flamboyant solution. They retreated in early middle age to twin beds: perfectly pragmatic – two times 3ft wide is considerably more than once times 4ft6in – but somehow now unthinkable. The very phrase "twin beds" conjures up in my mind only images of denial, distance and quiet despair.

Installing them would therefore be tantamount to a public announcement that all passion is spent. Opting for a king-size or super-king, by contrast, delivers exactly the same yearned-for personal space, while simultaneously allowing no suggestion that the flame isn't still burning bright.