David travelled with the 12th Doctor for a short amount of time, but both of their lives have been connected for quite a long time. David was first seen as a main character in Season 1 Episode 6. He was the Captain of the expedition that was led to the moon of Antiok. It was there that he met the Doctor for the first time initially, but in reality he had met the Doctor on one other occation, whether David knew this is unknown. David escaped the moon with the Doctor and Zack and was brought back to earth by the Doctor. It was told that the Doctor was going to ask him to join him in the tardis, but after learning his name he decided it was best not.