Re: I worked for free
"I started my working life as an independent professional (I won't say which discipline)"
Clearly a mercenary.
"People did not like my fees. They were three to five times what the natives charged and I always made it clear that after I finished things could go your way or against, depending on my findings."
Possibly even an assassin.
"I went to see this client, and as he was signing the cheque (remember those?) prior to my handing over my report, I mentioned the amount of tax he had been overpaying for the last fifteen years and how to claim it back."
"This wasn't what I had originally been hired for but when I saw this, it only took a little extra to put together the documentation for the guy to make his claim."
Ah Ha! Accountant who became a mercenary. Possibly after fighting his way out of compliance wit a spike made from a rolled up financial times.