The lines quoted by Inspector Cockrill and Mr Eden come from 'The Merchant of Venice,' Act 5 Scene 1.
Alastair Sim would play another eccentric police officer in An Inspector Calls (1954) eight years later.
The BBC used the plot of this for Father Brown (2013) series 4, episode 6, The Rod of Asclepius (2016).
Although a popular literary detective who appeared in six mystery novels, Christianna Brand's hero only appeared in this movie.
In the UK, surgeons, even though they have graduated medical school like all other physicians, are traditionally called Mister (or Miss or Mrs.).