When she asked what grandpa Ernst did in the Third Reich, Katrin Himmler’s father used to tell her that he was basically an apolitical man who was prodded into joining the Nazi Party by his elder brother, Heinrich, and took an innocuous job in German radio. Apart from that, Heinrich, the powerful head of the SS, had little to do with his brothers. For a long time this explanation ‘sounded plausible’.

Then, in 1997, Katrin’s father asked her to look at the Nazi Party files that had recently been returned to Germany by the Americans. For reasons she does not quite explain, he wanted to see if they shed light on what his father and uncle got up to while their brother was achieving notoriety. Katrin quickly discovered that the ‘plausible’ version was full of cracks.

Her grandfather had joined the Nazi Party in November 1931, well before Heinrich became eminent enough to inspire or bully his brothers into signing on. Ernst joined the SS two years later, just when he landed the new job at German Radio. This was no coincidence. Correspondence showed that, far