“Between sips of kale juice at the Soho Grand, a chic Manhattan hotel near her apartment, she is explaining to me why time has hardened our view of adultery.

‘It’s because fidelity is the last thing left that defines a marriage,’ she says. ‘You don’t need to wait to have sex, you don’t need kids. You don’t even need marriage anymore. The only thing that distinguishes it is that, after years of sexual nomadism, you suddenly say ‘I have finally found the one. You are so extraordinary that I am no longer looking for anything else. For you I promise to be suddenly exclusively monogamous’.’ The only hitch, says Perel, is that sexual nomadism doesn’t prepare you for exclusivity. ‘It’s not as though you got it out of your system. Love and desire aren’t the same thing.”