Stephen Tyas is a freelance researcher and author specialising in Nazi security police operations in Europe during 1933-1945. He has written extensively on the Holocaust and post-war activities of Allied intelligence agencies employing Nazi war criminals. He has given papers at seminars and workshops in Europe and the USA. His first book, co-written with Peter Witte, Himmler Diary 1945 (2015), was followed by SS-Major Horst Kopkow: From the Gestapo to British Intelligence (2017).