Survivors and world leaders gathered at the former Auschwitz extermination camp on Monday to mark 75 years since its liberation. 

The memorial in Poland is considered the most infamous symbol of the Holocaust perpetrated by Nazi Germany against some 6 million Jews during the Second World War. 

Those who survived it have tried to educate successive generations about genocide. But for some, the resurgence of right-wing populism across the world has familiar and worrying echoes.