Class statements and Sexism
The film makes some really great observations about class and gender. Class is mentioned quite often by Barbara, Sheba mentions it, as does Stephen. Interestingly, there is a distinction between class and "classy behaviour", the irony being that the highest of class (Sheba) shows the least classy behaviour (sex with a minor on the ground in a rail yard). Despite Barbara's frequent quips about class, she appears to be the biggest snob in the story.
Sexism is also evident in the story, particularly of the role of women, with the males of the story getting away with whatever they like. Eg, Richard is not overly judged for marrying a younger woman, and Stephen's parents, as well as Richard, cannot accept that Stephen played an active role in the scandal, referring to him as an "innocent", which he was not. Women are further downgraded by the Christmas dinner guest's (Sheba's mother?) comments about Sheba's father being "exceptional", while she simultaneously and blatantly plays down any virtues that Sheba might have.
In the closing scenes, I particularly liked the juxtaposition of Barbara's downward staircase, against Sheba's elevated ascent into her middle class, city home. It really just summed it up. Perhaps Barbara's fault was that she never aimed for more, preferring to position herself in the "front row seat" of life's soap opera.
All in all, if you're a middle aged woman, or an aged woman with lesbian desires, as Barbara was, it is plainly obvious you are at the bottom of the food chain!