Valiant (aircraft carrier)
The Valiant was a large flying aircraft carrier used by UNIT in the early 21st century. It contained various rooms including a conference room and many engine corridors. It was kept secret from public knowledge but politicians such as the President Winters of the USA and the Master as Harold Saxon, Prime Minister of Great Britain knew of it.
Every detail of it was designed by Mr. Saxon, and it was used for the first Human contact with the "Toclafane". (DW: The Sound of Drums)
In the following year in an erased timeline, the Valiant formed the base of operations for the Master, the Time Lord rarely visiting the Earth below. Both the Jones family (with the exception of Martha Jones, who had teleported to the planet below to wander) and Captain Jack Harkness were imprisoned on the ship, as was the Doctor. It also held the paradox machine inside the Doctor's TARDIS. When the timeline was erased, the Valiant was the only point in space and time not to revert, instead moving directly through time, due to it being the "eye of the storm", that is, the paradox machine. (DW: Last of the Time Lords) The Valiant is mentioned again by Martha Jones. (DW: The Sontaran Stratagem).
UNIT used the Valiant's turbines to clear the ATMOS gas, and to shoot the ATMOS factory. (DW: The Poison Sky)
