Woman goes back into office to pick up car keys she'd forgotten. Sees husband, who is also boss, snogging younger female colleague.
Later in the film, after he has tried to stop her leaving and attempted to control her, she screams at him that he can keep on trying to have her, but there's one bit he will never get, this bit in here (gestures to chest).
I have a vague idea the woman's played by Juliet Stevenson, but the only remotely likely imdb entry for her is a 1992 BBC adaptation of A Doll's House (which I'm not familiar with). The film was certainly contemporary, not period.
Any ideas?