‘Humans are the greatest single driver of climate change and greenhouse gas contributions, of deforestation and the acidity of the oceans,’ she explains earnestly.

‘The only thing that will fix these problems is to have fewer people on the planet. I don’t see it’s justified to make more people than we already have. Yes, I have a maternal instinct, but I will never change my mind.’

Drastic? Perhaps. But, astonishing as it sounds, Oonagh is one of a number of British women who are deciding to remain child-free, not because of career aspirations or an inability to find a partner, but because they are concerned about the crippling impact of overpopulation on the Earth.