WHEN MY SON JOE was young we passed a particularly ornate church, and I pointed out the flying buttresses on the outside. Naturally, being of a curious nature, he asked what they were for. So I showed him.
We both stood up and I got him to raise his arms and grasp my hands above his head. We were the walls of the church, I explained, and our arms are the roof. Now the problem is that roofs are heavy, and they exert a downwards and outwards force on the walls.
So saying, I pressed on his hands. To stop himself falling he naturally moved one leg behind himself.
‘And that,’ I explained, ‘is a flying buttress.’
