Cliff Boxworth was the Mission Commander of the Apollo 11 mission to the Moon from the Kennedy Space Center in July 1969. He signed on the mission to put a man on the Moon, asking Agent Milledge, "Who needs anything more?" When the Tenth Doctor was imprisoned by Milledge and Spencer, Cliff wished to help the Doctor sooner, saying "as much as I like you, Doctor, my first priority is to the men in that capsule."
He took the Doctor out on 20 July and showed him the back exit to Mission Control so he could reach the TARDIS. Before leaving, the Doctor explained his plan with the dictaphone to Cliff and Justin; the recording had an alien language on it. He intended to feed it through the TARDIS' "very sophisticated translation computer", which would create a visualisation of the sounds. The Doctor would then place the visualisation where the aliens, who had tried contacting humanity, would see it. On the Moon, the Doctor asked the aliens to leave, telling them that humanity needed to find their own way. With no trace of the aliens on the broadcast of the Moon landing, the agents had no choice but to let Cliff and Justin go. (PROSE: Blue Moon)