We have different approaches to tidying up, my wife and I. It bothers her very much that the house we share with three chaotic children is so untidy. Over the years unsightly, useless, out-of-date items accumulate in every room: incomplete jigsaws, dried-out paints, barely-played boardgames, broken furniture, too-small and obscurely stained clothes, collections of shells and pebbles, or that vibration-sensitive fluffy penguin which flaps its stubby wings and blares out a tinny version of ‘Rock Around the Clock’ when a spider stamps its foot anywhere within a kilometre of it.