This was really hard to write for some reason. I re-watched the movie yesterday and it struck me how everytime Billy went out on a job for Costello he wasn't assigned to Fitzy or Delahunt, but to French - as if maybe French wanted it that way. And not necessarily because of lack of trust (although a case could be made that way), but perhaps because he trusted Billy more than the other two. So that's where it came from.

Glad you liked it!