Originally Posted by
spekesoftly
Gatwick's second runway, built in the 1980s, is an exception. It cannot be used to increase capacity (at present!) because it is too close to the original southern runway for simultaneous use, but can be brought into to use during periods of maintenance or an incident blocking 26L/08R.
I have no experience with Gatwick however I bet The second runway there can be used to increase capacity. At such airport where parallel rwys are too close to allow for simultaneous approaches, One is used for departure and other for arrivals. This increases capacity because it allows for one aircraft to line up while the other is still on approach. As the landing aircraft touches down, the departing aircraft can commence takeoff.