The opening hanging scene has a public hanging using the large American style knot, which was never used in Britain. Prisoners were given a black cap, instead of a white. Furthermore, the last public hanging in Britain was in 1868, 32 years before the movie is set.
The film is set in 1900 but Lestrade accuses Farrington of being a "Bolshevik", a term that didn't come into use until 1903.