In the1980s when I worked as a paediatric psychologist, I remember an eight-year girl who in the course of play therapy imaged herself in drawings dressed as a boy and selected those toys/games usually identified with boys. There was no convincing otherwise, and insisted on giving herself a boy’s name. Four decades on, psycho-biomedical science has advanced, and we are learning much more about human sexuality – but not enough to satisfy the inquiry into all its presenting variants. A recent documentary by Sebastien Lifshitz, Petite Fille (2020), illuminated the moving true-life story of seven-year-old ‘Sasha’, born male, but when she was barely three years of age knew she was really a girl.