Gatwick expansion - how can it take 5 years?

I can totally see how Heathrow expansion is at least decade away, it’s bloody complicated for starters. But I looked up the Gatwick expansion plans today and I can’t believe how uncomplicated it is. Can someone explain how Gatwick moving it’s runway by 12 metres further north can take 5 years of building.

I can totally see how Heathrow expansion is at least decade away, it’s bloody complicated for starters. But I looked up the Gatwick expansion plans today and I can’t believe how uncomplicated it is. Can someone explain how Gatwick moving it’s runway by 12 metres further north can take 5 years of building.