Sharing your life with someone used to mean sharing your home with them.
But one in 20 couples now chooses to live separately, according to research.
The number of men and women ‘living apart together’ has increased by 40 per cent in the last decade, and it is thought that around one million couples now keep separate properties.
Actress Helena Bonham Carter, 44, and film director Tim Burton, 52, are among them, living in adjoining apartments in Hampstead, North London.
The couple, who have been together for more than 10 years since meeting on the set of Planet of the Apes, have separate kitchens, their own televisions, chintzy decor for her and gothic furnishings for him.
The survey, carried out for Halifax Home Insurance, suggests that young couples live apart because they are reluctant to sacrifice their independence, while those who are older have accumulated too much furniture and too many possessions to squeeze into one home.
But there is an ongoing debate between politicians and economists over whether the phenomenon is down to growing independence – or increasing benefit dependence.
Many are thought to stay apart because of the ‘couple penalty’, which means that a man and a woman face losses in tax credits and means-tested benefits if they live together.
The bias against couples in the benefits system means that, according to calculations by the independent Institute for Fiscal Studies, a single mother misses out on an average of £100 a week if she moves in with a partner, and this can rise as high as £200 a week.
But the Halifax report suggests that men are more likely to want to delay cohabitation than women, and those who live in cities are more likely to share a home than countryside dwellers.
The price of living apart may be higher than many couples realise, with those who commute between each other’s homes three times more likely to be burgled than those who share a property.
The research, based on a survey of 2,000 respondents, found that nearly one in five of couples living apart are over 35. It said: ‘The primary reason for adopting this living situation differs by age.
‘Younger couples mainly fear rushing in to live together, while over-35s are most likely to resist a life under one roof because they have too many joint possessions to fit into either property.’
The Office for National Statistics has put the official number of couples ‘living apart together’ at 1.2million.
It delayed publication of its analysis in the mid-1990s, largely because of concerns over the political impact of the high numbers when there were growing fears that the benefit system was promoting single parenthood.
A study for the Royal Economic Society last year connected tax credits with marriage break-ups, saying that divorce rates had risen among low-income couples since the introduction of the credits in 1999.