Prison guard (The Impossible Astronaut)

This Prison Guard was a human guard (we assume he is human) at the Stormcage Containment Facility. He reported that River Song was packing her belongings (again) after she received the TARDIS blue invitation sent by the Eleventh Doctor. He told the person on the other end of the line that River said she was going to "some planet called America". (DW: The Impossible Astronaut)