In the vintage Monte Carlo scene which opens the movie, when Larita first sees John both her and John's movements are slowed down while the rest of the cast play at 'normal' (i.e newsreel) speed. This was accomplished by filming the crowd, Larita, John, the background and the foreground mechanics separately against green screen and compositing them together at different speeds.
Though not expressly stated, the story gives the impression that Larita is somewhat older than John (she repeated refers to him as a boy). In fact, Jessica Biel is actually younger than Ben Barnes by several months.
During the end credits all of the musicians who played in the orchestra featured on the soundtrack are introduced in voice-over simulating the introductions from the bandstand of a live performance, with each musician playing a brief sample.
In the scene prior to the party when Jessica Biel is in her bedroom smoking, and Colin Firth walks in, Jessica is smoking a filtered cigarette (one can tell by the white, rather than brown, end). This is most unlikely since the first usable machine to make mass-produced filter cigarettes wasn't even invented until 1935.
In the scene where the newlyweds arrive at the family estate, a footman unloads their luggage from the car. The suitcase shown is a Halliburton aluminum case, which wasn't available to the public until after World War Two, despite the film being set well before that war. The model shown was actually produced in the mid-1950s through the 1960s.
(at around 17 mins) Jessica Biel is referred to as "where is our beautiful cougar hiding" by Charlotte Riley. The term cougar meaning a predatory older woman was first used in Canada in 1989 and was certainly unheard of at the turn of the last century.
How much sex, violence, and profanity are in this movie?
A
For detailed information about the amounts and types of (a) sex and nudity, (b) violence and gore, (c) profanity, (d) alcohol, drugs, and smoking, and (e) frightening and intense scenes in this movie, consult the IMDb Parents Guide for this movie. The Parents Guide for Easy Virtue can be found here.
Q
Is this a period movie?
A
The movie is set in the 1920's, just like the play.