Central City was the capital city of Earth that existed by the 28th century. It encompassed the whole lower half of England, including London. (TV: The Sensorites) By the 30th century, the Seventh Doctor explained that it was "Spaceport Five Overcity," which used to be known as "Central City," and before that as "London." (PROSE: Original Sin)
In the third quarter of 3950, Mavic Chen was elected as Guardian of the Solar System in Central City. (AUDIO: Neverland) The Space Security Service had its headquarters there. (TV: The Daleks' Master Plan)
According to one account, rather than being in England, Central City was located in New Washington. (PROSE: Mission to the Unknown)