Our fascination with treehouses has deep roots

You can’t (and probably shouldn’t) design a treehouse. Treehouses should grow organically, in every sense: they must be made of wood, obviously — one definition of a treehouse is that it is a tree holding its dead friend — and the footings for the platform must be the knots or branches that are footholds when climbing the tree. Besides, it is only when you are halfway through building that you can work out where you need to fit round branches and add noggins — unless you build it between the trunks of two separate trees, or use some sort of 3D mapping software, both of which sound very much like cheating.

So there wasn’t any masterplan behind my son’s treehouse. I bought some 2x4s in the first lockdown — timber merchants were the only shops open — and fitted them together in my head and the tree. My son had his own amendments (he thought that there should be a rope ladder he could raise and a trap door he could shut to escape from his enemies, which seemed like a very sensible precaution) and I had mine.