The plot is based on the Rattenbury murder case, which I had also not heard of previously, but which is pretty much Thompson-Bywaters redux, though with a crucial difference in the social class of the woman. Alma Rattenbury (Duff), louche 30s songwriter, is accused of the murder of her husband** with her 18 year-old lover, Percy Stoner. Her story - the narrative concentrates very much on her, and takes Stoner pretty much at face value as a bit of cheeky chappy rough trade - is paralleled with that of presumably not also RPF jury forewoman Edith, who is divorcing her husband because she won't have sex with him, and he cheats***. Edith's family is falling apart around her because of her 'principles', but it is the ultimately thought-through rather than instinctive prinicples that allow her to judge the case. Though we do not, in fact, ever know quite what "really happened". There was a lot of comedy, not least in the trial scenes of the second act - I am quite tempted to read the transcript to learn whether the actual court speeches had quite so much of the Thorpe and Archer cases about them (notwithstanding that they came afterwards). I am only sorry that I saw it too late to recommend it in time for others to go themselves.
The play also contains an important message to parents: lose no opportunity to take your son to a French brothel or see him seduced by a married woman, otherwise he will end up with a Social Disease and a nervous breakdown. Which leads me to ask oursin, the fount of all knowledge on such subjects, what treatment the unfortunate ?gonorrhea-suffering son is undergoing twice-daily in the bathroom with the tap running.
*I had read one of his plays, the one on Alexander the Great and Philotas, in a Mary Renault phase.
**Who was a notable architect according to Wikipedia, not that you would know this from the play.
***I don't recall whether it was clear if the sex stopped or the cheating started first. But the authorial sympathy with the husband who wants the facade of marriage and to play around (Edith is willing to divorce him), struck me as rather 70s. Also, as he was chucked by his lover (something we are meant to sympathise with him over) it did strike me to wonder if there's a reason there that Edith has no interest in sleeping with him.