- You may be looking for the Viking.
Lofty was an oak tree at Sydenham. One day it was taken over by an alien which was sucking away the potential, ambition and motivation of the people near it and fed from it. Mrs Mann called the tree Lofty.
During the 18th century Lofty was a gallows tree where criminals were executed.
In 1940 Lofty stood in the garden of No.1 Gallows Gate Road. It locked out all the light to several rooms. Mrs Mann wanted to cut it down for several years. However, she didn't do it. It turned out that the alien took her willpower to do so. It also took the energy and strength of all the other residents of the house.
The only resident of the house who was not affected by the alien was Robert Mann. Robert still hadn't decided what he wanted to be in life so the alien had no ambition to feed on. The Tenth Doctor told Robert that Robert was the only one who could cut down the tree. Robert did it and the alien left the tree while the other residents got back their ambition. (PROSE: Number 1, Gallows Gate Road)