Who is Arthur Koenig from The Prestige and what is their importance?

Arthur Koenig is a reporter. He meets with Angier to interview him on his performance. In the middle of their interview, he asks about Angier's theory that Borden is using a double in his show, revealing that he has confirmation that Borden has no twin. He also provides Angier with a great deal of information for Angier to use to dig up the truth about the illusion of the New Transported Man.