Denis Avey - who is now 91 - spent the latter stages of the Second World War as a prisoner of war in a camp adjoining Auschwitz. Working alongside the starved and brutalised Jewish inmates of the concentration camp, he decided to try to help them.
He swapped places with one inmate, spending two nights amid the full horror of "hell on earth". For the first time, Mr Avey has agreed to a television interview to talk about what happened to him. The BBC's Rob Broomby met him.