Oliver Morgenstern

Oliver Morgenstern was a medical student at Royal Hope Hospital. He was on duty in the hospital when it was transported onto the Moon by the Judoon.

He kept following the Judoon captain and reassuring the patients that they were safe. When the hospital was back on Earth, he was being interviewed on the radio. (DW: Smith and Jones)

Alternate timeline
In an alternate universe in which Donna Noble created by turning right to the wrong job interview. The Doctor died on Christmas eve 2007, thus he would not have been able to save everyone in the Royal Hope.

Oliver therefore was the only survivor and Martha Jones gave her last breath to save him. (DW: Turn Left)