He is known to spend a good deal of time at the shop

Stephen Bates at the Guardian on Special Branch's decades-long monitoring of George Orwell and others:

A Sergeant Ewing of Special Branch, monitoring Orwell's attempt to recruit Indians to work for the BBC's India service in January 1942, noted: "This man has advanced communist views ... He dresses in a bohemian fashion both at his office and in his leisure hours."