Poul Anderson's Trygve Yamamura is a private detective, Anderson's Dominic Flandry is a spy and Stieg Larsson's Mikael Blomkvist, whom I mention for comparison because I am rereading Larsson's Millennium Trilogy, is an investigative reporter. Thus, all three characters seek to uncover hidden information. However, they serve different interests. Blomkvist usually publishes what he learns whereas Flandry reports to his superiors who, he knows, use the media to mislead the public.
Here and now, I would feel at home helping a magazine like Blomkvist's Millennium but not helping British Intelligence! It is reported that intelligence services use torture and it is real life equivalents of Blomkvist that do the reporting. Blomkvist investigates a serial murderer and a clandestine branch of Swedish Security so there is a distinct overlap between the three levels of inquiry but I prefer someone who reports to us, the public, not to our political lords and masters.