Should the "F" in "Farmer John" be capitalized mid-sentence?

Question

I'm writing story-generating software. One specific story involves a farmer with a variable name. I'll use "John" as an example. For a "folksy" or "old-timey" or "child-targeted" sound to the story, I always refer to the character as "Farmer John" instead of just "John."

Starting sentences, it's clear that the "F" in "Farmer John" is capitalized -- but I'm unclear whether the "F" in "Farmer John" should be capitalized mid-sentence as well.

E.g. which of these is correct, and why?

Martha sees Farmer John building a barn.

Martha sees farmer John building a barn.

My doubt is because in the context that I'm using "Farmer John", it feels as though the entirety of "Farmer John" is a name/pronoun, therefore both words deserving capitalization -- but I can't claim anything other than a gut feeling to legitimize that.

Answer 1

1. Martha sees Farmer John building a barn.

2. *Martha sees farmer John building a barn.

To be correct, the second should be

Martha sees the farmer, John, building a barn.

You are writing it and have chosen the name of the character as "Farmer John" - as opposed to say, "John Farmer" or "John Smith".

Its a name - it's capitalised.