He was born in Austria to Jewish parents. After the 1938 Anschluss with Hitler's Germany, he was put on the first Kindertransport train to leave Vienna. He was initially housed in a refugee camp at Lowestoft in England. After this he lived with a Jewish family, who were West End tailors in London. Grunberger entered their tailoring business. His desire for education however led to his taking A levels at Birkbeck college. He gained an exhibition scholarship in history at King's College London.
When he went to the Wiener Library in London, he expressed to a friend his frustration at the absence of a book that held together the masses of documentation surrounding Nazism and 20th-century Germany. A friend asked why he did not write one, and so he did. The product was A Social History of the Third Reich, first published in 1971 by Weidenfeld & Nicolson. It has since become a significant text for studying the social history of Nazi Germany in schools and at undergraduate level.
A Social History of the Third Reich
Red Rising in Bavaria