There are many historical inaccuracies in this film, but neither the film makers nor Robert K. Massie, whose book this title is based upon, can be held responsible for the inaccuracies in regard to characters and events. When Robert K. Massie initially researched materials for his book, the Soviet government was still in power in Russia and would only authorize viewing of those "facts" that had been assumed by people and "approved" by the then ruling government to be examined by researchers of the Romanov family. It was not until the Soviet government fell in 1991 that documents that had been secreted away and which were hidden from the public could be fully examined and researched.
For many years it was believed that Prime Minister David Lloyd George's wartime coalition government would not allow the Romanovs to come to the UK after the first revolution in 1917. However, many years later it was confirmed that it was actually King George V who was against the idea due to the possibility of unrest similar to the previous year's Easter Rising in Ireland. The King forced the government to withdraw its offer of asylum to the Romanovs, in an apparent abuse of his position as a constitutional monarch.
The character played by Curd Jürgens is Arthur Zimmermann, the German Foreign Secretary who was instrumental in trying to arm rebellions in Ireland and India during World War I, as well as offering a military alliance with Mexico which caused the United States to enter the conflict.
Press reports at time of pre-production said that Rex Harrison and Vanessa Redgrave were to appear as the leads. However, a recent biography of producer Sam Spiegel stated that paperwork (in an Israeli museum) belonging to Spiegel shows that he never offered them the leads.
Despite the massive box office success and critical acclaim that Sam Spiegel had brought Columbia with " On the Waterfront", " The Bridge on the River Kwai ", and " Lawrence of Arabia", the studio were unwilling to give Spiegel the budget he needed due to a string of recent box office failures including " The Chase " and " The Night of the Generals ".
The execution scene proved to be emotionally taxing for Candace Glendenning (Marie). Glendenning claimed that she had gotten so "caught up in the story" and drew a close bond with the cast that she had felt they were all a real family. During the actual execution scene Glendenning broke down in tears on the set and had to be taken backstage to be given a cup of tea to settle down before she could return to film again.