a poacher turned gamekeeper

a poacher turned gamekeeper

  (British)
someone whose job seems to involve working against the person who is now doing the job which they did before
Usage notes: A poacher illegally kills and steals animals on someone else's land, and a gamekeeper's job is to stop this from happening.
He used to be the the union rep but now he's in management - a case of poacher turned gamekeeper.
See also: gamekeeper, poacher, turn
References in periodicals archive ?
Bill, 59 Northum definitely gamekeep"I th 59, from Ashington in Northumberland, said: "I'm a poacher turned gamekeeper.
He said: "That was very enjoyable at the time but perhaps I am a poacher turned gamekeeper now that I'm back in the city centre.
The LAPD, obviously having better things to do, pass the buck to Roth's insurance company who in turn hand the investigation to the rugged Sam Levitt - effectively a poacher turned gamekeeper.
Sometimes in the security business you need to employ someone who is a poacher turned gamekeeper.
Mac is like a poacher turned gamekeeper, " he said.