His grandfather was a court jeweller and his father, Otto, was an officer in the German Army during World War I[1] who died during routine surgery while Koch was still an infant.

Koch was deported to Canada where he remained at an internment camp in Sherbrooke, Quebec until 1941 when he and most of his fellow internees were recognised by the government as "victims of Nazi aggression" and released.

[3] He retired from the CBC in 1979 in order to focus on writing books and teaching at York University, where he was a course director in the Social Science Division and taught a course on The Politics of Canadian Broadcasting for 18 years, into his eighties.

[2][5] Hilmar and Odette, the story of two of his half-Jewish relatives who remained in Germany during World War II and their contrasting fates, was awarded the Yad Vashem Prize for Holocaust Writing in 1996.

[3] His historical fiction has been set in the recent German past, particularly the period from the late 19th century and into the Weimar Republic, and has been published in Germany as well as Canada.