Gatwick plans to rebuild its existing backup runway just far enough away
from the main runway to permit simultaneous use of both runways. The
shorter second runway would only be used for short haul take-offs.
Additional taxiways and stands will be needed, but no new terminal. The
airport still seeks to add another, full-length third runway and additional
terminal to the south.

https://www.thetimes.co.uk/article/gatwick-unveils-bn-plan-to-move-runway-12-metres-gntjsh8b5?shareToken=e7b73eb686822019d2230f77f64cc 316