Think moving in together is stressful? Try it in No 10!

MOVING in with each other is a big deal. Imagine, if you will – though I’ll forgive you if you’d rather not! – being Boris Johnson and Carrie Symonds negotiating their new status as the first unmarried couple in 10 Downing Street at the same time as being two of the most scrutinised individuals in the land.

Most people in a relationship as relatively new as theirs might still be wondering whether it’s too presumptuous to leave a toothbrush at the other’s flat.

Although they’ve been living together for months, shacking up in your girlfriend’s pad when you’ve moved out of the marital home is not at all the same as moving in together. That’s just a holding pattern. It’s when one person’s stuff – their clothes, furniture, shaving foam, vinyl collections, books, cracked china, and souvenir shot glasses – has to merge with the other’s that you know you’re in it for the long haul.

In Boris and Carrie’s case they will be helped by the fact that Downing Street is neither’s original home. There’s no one person who will have the sense of their patch being invaded. Even if the invader is someone you dearly want to be with. And I doubt Boris is going to kick up too much of a fuss over the colour of the new curtains.

But sharing domestic life is never entirely simple. As one half of an unmarried couple, I remember how pleased I was when David decided to move in and live with my son and I – although typing that now I realise that moment didn’t actually happen. Somehow, he was just there. Along with an increasing amount of his belongings.

I had no concerns at all about whether we would be happy living together but where to hang his pictures – his collection of 1960s posters was going to need some dealing with – was something else. Luckily, David is almost St Francis in his lack of interest in possessions but even so we have had our moments. A collection of huge photo books of naked yogis anyone?

There’s also the inescapable fact that romantic relationships when you live apart have the built- in advantage of allowing you to look forward to being with each other. Living together takes a sledgehammer to that. Delightful as it is to be in your loved one’s company, few would claim that sharing the bathroom sink day in, day out is one of life’s great aphrodisiacs.

And it denies either of you an escape route at those times we all have when you can’t stand the sight of the other. Passionate arguments are much easier to deal with if one of you can slam the door and retreat to your own home for, in the phrase of the moment, a period of reflection.

A solution no longer available to our first couple next time the Prime Minister drives his girlfriend mad – or when he spills red wine on the pristine white sofa…