Final answer:
The subject of this question is English, and it relates to a literary work or text involving law enforcement and investigation.
Step-by-step explanation:
In this question, the subject being addressed is English. The information provided states that Mr. Jones was referred to as 'the official police agent' and that he was the lead detective of the Scotland Force. This suggests that the question is related to a literary work or a text that involves law enforcement and investigation.