People have always been flattered by having their positions start with a capital letter. It marks them out from their subordinates, and makes Persons look Very Important. Anyone from The Queen down to the Area Manager can access an exclusive capitalisation club that is ever out of bounds to the cleaners, sales assistants and copywriters of the world.

But at what point is it wise to stop? If the Area Manager is capitalised, should the Branch Manager? The Assistant Branch Manager? The Team Leader? And if the Chairman of Shell gets a capital, should the Chairman of Bob’s Plumbing Services (Bob)?

In general there’s a downward trend in capitalisation that has mirrored the overturning of deference in society. It’s common to see the prime minister in lower-case, so you can feel safe putting the department head next to him or her.

One interpretation follows that if you’re using the name of the position instead of the person’s name, you should use capitals, but if you’re talking about the position in general it can be lowered.

Titles in formal contexts

The lower-case trend does not apply when dealing with people’s individual titles in formal contexts. So we’d have Professor Ian Lee and Liz Smith, Marketing Coordinator.
Writers and editors still overcapitalise, probably because they don’t want to offend someone.

But when you’re just describing a position in general prose, it’s fine to use lower-case initials.