What is "copper's nark"

Usage examples of "copper's nark".

I'm no copper's nark, to look down my nose at a revolutionary like Walter Gerard -- no matter what the Rad Lords may call him now.

I'm no copper's nark, to look down my nose at a revolutionary like Walter Gerard—no matter what the Rad Lords may call him now.

I'm no copper's nark, to look down my nose at a revolutionary like Walter Gerardno matter what the Rad Lords may call him now.

A pickpocket, supporting his old age as a 'copper's nark', brought news of him to the local detectives.

I'm no copper's nark, to look down my nose at a revolutionary like Walter Gerard--no matter what the Rad Lords may call him now.