Who would the assistant partner of an inspector be called?

Question

Is it correct to refer to the partner as the assistant partner of the inspector??
And would the partner be a sergeant??? And if so, would the man be called Sergeant [his surname] or can you just call him Mr. [surname]???

Answer 1

In Inspector Morse, it does seem that it Sergeant, and they are referred to a Sergeant Lewis, but no doubt he answers to Mr Lewis occassionally.

Answer 2

INSISTANT