From Halopedia, the Halo wiki
This interviewer is an unseen character in the Believe live-action shorts for Halo 3. Although he is not seen, his voice is heard; he sounds like a middle-aged man with an English accent. He interviews some retired soldiers about their experiences during the Human-Covenant War. The interviews take place at the Museum of Humanity; it is quite likely that he works there. However, he is also seen out in the woods during one of the shorts. He also narrates the history and the background for the Museum.
List of appearances