Factual error: When the Duke of Oxford (Ralph Fiennes) meets Rasputin, he notes how he "mastered the Bryozka glide", a dance technique where the practitioner looks like they are gliding a few cm over the floor instead of walking. However, while the scene is set in what must be 1916, the Bryozka glide was only invented in 1948 by Russian ballerina and choreographer Nadezhda Nadezhdina, who founded the Beryozka Dance Ensemble. (00:44:10)
Factual error: The Black Watch sergeant major wears a crown over three chevrons, which was the correct rank badge for a company sergeant major until 1915. However, this is at least 1916 (as conscription has started and the men are wearing steel helmets, both introduced in 1916). CSMs had been redesignated as warrant officers in 1915 and now wore a crown on the lower sleeves instead.