Under the 1913 Mental Deficiency Act, Britain imprisoned 50,000 people as “moral imbeciles.” Many of them were young women—working class, poor or unwed mothers, often victims of sexual assault—and most were confined to so-called Mental Deficiency Colonies for the rest of their lives. It was all down to eugenics; as the middle-class birth rate declined, Britain feared the working classes would outbreed their “betters,” so they imprisoned certain sexually active young people to keep them from having children. Not unlike Ireland’s Magdalene Laundries, the Mental Deficiency Colonies were places of terrible abuse. Today we talk about this terrible chapter in British history with Sarah Wise, author of The Undesirables: The Law That Locked Away a Generation.