At airfields, such as Gatwick, an ATCO might speak to maybe 60-70 a/c in one hour.
At airports, such as Heathrow, an ATCO might speak to 120+ a/c an hour.
So dividing those numbers by the number of runways in use (and bearing in mind one controller per runway); You are admitting that Gatwick is at the very least, as busy as Heathrow
Certainly confirms the fact that Gatwick is the busiest single operation runway in the world.