The sound of the judge banging a gavel is heard several times in the courtroom scenes. In England only auctioneers use gavels; judges have never done so.
Edith buys an orange 2d stamp which she attaches to a letter she then posts. Earlier in the film there are close-up shots of letters with single 1d red stamps attached. The one-penny rate for letters ended in 1918.
There are references to Rose's daughter been taken off her by the CPS; a modern organisation that begun in the 1980s.
After Edith collapses at the trial the judge says "We'll convene there" when he means "We'll adjourn there".
CPS (Child Protective Services) not only did not exist in 1920s England, but it is an organisation that only exists in the modern USA. According to a newspaper article of the time, Rose was instead reported to the Inspector for Cruelty to Children.
The UKs first female Asian police officer did not serve until the 1970s.
Rose and Nancy buy an ice cream on the beach and the ice cream seller says 'Enjoy'. Using enjoy as an imperative only started in the 1980s or 1990s. In 1920 they'd have said (correctly) 'Enjoy your ice cream'.
The Judge presiding over the case is black. The first black Judge in England and Wales was not appointed until 2004.