So why does population control hardly feature on the agendas of the UN bodies or of the governments now committed to tackling climate change? And why do the development and environmental groups shy away from it? The Guardian’s George Monbiot dismisses the topic as a distraction, the obsession largely of “post-reproductive, middle-class white men… a group more responsible for environmental destruction than any other class in history”…

But how do you reduce population in countries where women’s rights are already achieved and birth-control methods are freely available? Could children perhaps become part of an adult’s personal carbon allowance? Could you offer rewards: have one child only and you may fly to Florida once a year?

After all, based on current emissions and life expectancy, one less British child would permit some 30 women in sub-Saharan Africa to have a baby and still leave the planet a cleaner place.