I once had a tree house. My father and my best friends’ father built it into the majestic fir tree in our garden. I still picture them, fathers of two six-year old girls, wearing chequered flannel shirts and old jeans. They worked the entire summer weekend: sawing, drinking sips of beer, hammering together boards of wood. At the end of the weekend they had created an impressively large wooden platform, hidden under the wide branches of the fir tree.