When she was young, my great aunt – a tiny sprightly woman who painted vast canvasses –  had wanted to become a nun. Then she met a Flemish poet and they fell in love. She agreed to marry him on one condition: that they have 12 children. True to the old baking tradition, they made 13.

Her niece, my mother, also briefly flirted with the holy life. Her tryst with celibacy was equally convincing. As the eighth of her brood, I approach the subject of global population with a touch of trepidation. By anyone’s standard of reasonable family size I really shouldn’t be here.