It's interesting to see the context in which these cases took place and worth quoting a paragraph from The Trials of Hank Janson which relates to prosecutions that took place in 1938-39.
In the year ending June 30, 1939, only 40 offences of obscene publications were recorded in the United Kingdom, mostly destruction orders issued against magazines and photographs originating in the United States or France; in only 9 cases did the offending material originate in the UK. Between July 1939 and December 1940, the number of cases was down to 47, mostly (36 cases) involving publications from abroad.I've always thought that one of the reasons those particular novels—Miss Callaghan Comes to Grief by Chase and Road Floozie by Glinto—were targeted was their American settings; it seems likely that police constables gathering up American magazines for possible prosecution would have grabbed everything that looked similar.
A few months earlier, on 6 October 1941, the New Picture Press Ltd. of Arundel Street, Strand, were fined £200 with £21 costs at Reading for publishing improper issues of the magazine London Life.
The push against obscene material may have been the result of this case and two prosecutions in late 1941 which resulted in jail sentences. At West Riding Assizes, a 53-year-old man pleaded guilty to the indecent assault of four girls and three charges of sending indecent photographs through the post. He was sentenced to three years. It was noted during the case that the guilty man had a developed his obscene photographic business by contacting customers through a publication readily available on bookstalls.
A case was heard a week later at Sussex Assizes about a case of attempted buggery and indecent assault and of sending obscene prints through the post. This case resulted in a sentence of four years.
These two cases followed almost immediately the appearance of a League of Nations Annual Report published in Geneva on 14 November 1941 on activity relating to obscene publications. As mentioned above, almost all the instances of trafficking stopped by the Post Office involved material coming into the UK from abroad, mostly France but also America, Finland, Denmark and Sweden.
It seems plausible that this "perfect storm" of activity led to increased activity in 1942 and fines being issued against Road Floozie and Miss Callaghan Comes to Grief in March and May 1942, followed by the prosecution of authors and publishers at the Central Criminal Court in May.
An interesting coda to the above case involved Detective-sergeant Sidney Norman who said that "all books of this type would in future be seized by the police, wherever found." In fact, only a handful of court cases against booksellers followed that year, at least two involving the continued sale of the two prosecuted books.