The Policeman was a police officer working in the London area.
The Policeman was alerted to the murder of The Blonde, who was found dead in her flat with her fingers broken and head smashed with a hammer. Around the same time, Bill turned himself into the police to admit robbing the safe of The Bald Guy. The police searched Bill's flat, findings several items belonging to the dead blonde woman.
The Policeman then interviewed Bill, who explained the story of how he met Cobb and started burgling flats with him, relating how Cobb was being suspected of the murder of an old lady and wanted to dress Bill up as a suspect. The Policeman then explained to Bill that they didn't have any such murders of old ladies on file, and they were in fact investigating the blonde woman's death. He then told Bill that they had found her blood on his hammer, and her belongings in his flat, and that he was the prime suspect in her murder.