Think of the most precious and intimate of your material possessions: your private papers, your CD collection, mementos of family long gone, bedside reading and even the warmth of your pillow and duvet. Imagine inviting strangers with whom you share no friends or even acquaintances to open your front door and take possession of all of this, for one whole week. If, as Adam Phillips and Barbara -Taylor argue in their new book On Kindness , most people seem to believe that deep down humanity is mad, bad and dangerous to know, this is indeed a very strange thing to do. Yet this is precisely what our family did over the new year holiday. We swapped our London house with that of a totally unknown French family, who live in an apartment near the Marais district in central Paris.

Like many people who take advantage of the growing number of websites offering home exchanges, my motives were mixed. As we have children, an apartment where the kids have their own room and we can cook for ourselves is always preferable to a hotel. Our French strangers reciprocated by sleeping in our beds while we slept in theirs, so no money changed hands. But the incentive was more than simply financial. For me, this holiday felt like I was embarking on a hazardous and yet exciting adventure. I was taking a risk - a risk of trust not just in one French family but in the notion of trust itself, of being kind to strangers.