The most inspiring voice on radio this week belongs to Hetty Werkendam, or rather to her 15-year-old self as she talked to the BBC correspondent Patrick Gordon Walker in April 1945. He was with the British soldiers who entered the Bergen-Belsen concentration camp and witnessed the horrors of that scene: dead bodies in piles with no one to bury them, living people lying beneath them too weak to move, or using them as pillows.