Doctor Who: The Space Age

It is England, Earth, in the year 2019. The Doctor, Fitz, and Compassion land on a bleak plain, near a derelict city where mods and rockers are converging to fight out their differences. While the Doctor is taken prisoner by the rockers, Fitz is whisked away by the mods. In the midst of the gang wars, can the Doctor find out what transported the mods and rockers to the derelict city and why?