Newnham College, Cambridge, was once a bastion of feminist activism. No longer. This summer my curiosity was drawn to two women whispering to one another in the college cafe. They were, as it happened, a senior fellow and doctoral student; leaning over their table, they spoke furtively for fear that someone might overhear their conversation about gender politics. At Cambridge, professors and students alike are afraid to speak critically, or at all, on the subject of gender. Believing that biological sex is binary and unchangeable – and that gender is culturally constructed – may not seem controversial. Yet gender-critical feminists who hold such mainstream views are often slapped with a derogatory label: Terf, or trans-exclusionary radical feminist.