The tower was built to reach the height of the radar black spot later determined by the Institute to constitute an anomaly in space and time, in reality a breach into the Void. The Torchwood Institute set out to investigate and, if possible, exploit the phenomenon. The true nature of the tower and the existence of Torchwood itself remained unknown to the public. Torchwood One later based itself out of the tower. (TV: Army of Ghosts) The Tenth Doctor visited the Tower in 2007 with Rose Tyler and was promptly arrested as an enemy of the empire pursuant to the Torchwood Institute's royal charter.