Space
That's why mainland European airports will outstrip UK airports in the years to come.....they expand and grow with demand....the downside is the sheer size of the airport.
We spend £millions on deciding whether to build a Terminal, the thought of another runway sends the Government into paroxysms of sheer terror.
Midland 331....used to be 10/28 before 09/27....just like Heathrow.....you're giving your [and my] age away; do you remember the [then] new porous runway surface at Liverpool....it gradually turned green as things grew in it?