In reference to Margaret's previous love affairs, David Niven is briefly mentioned, though in a very vague way. In fact, the future Duchess of Argyll became pregnant by the then-unknown Niven in 1928, when he was eighteen and she not quite sixteen. An (illegal) abortion terminated the pregnancy.
Maureen refers to the 'bonobo' ape. Although the bonobo was recognised as a separate species to chimpanzees in 1933 (instead of a 'pygmy' chimp), the name was not coined until 1954. This scene is before Margaret's marriage to the Duke of Argyll in 1951 so the reference to the bonobo is an anachronism.
Although Claire Foy, playing the Duchess of Argyll, was only in her thirties when making this mini-series, the real-life Duchess was past fifty at the time of the sensational divorce in 1963.