Asturias, 'why do they need to fly in?'
Good road access in London enables tactical movement for patients within the city.
LCY is more strategic air transport, moving people and equipment over longer distances, between airports, particularly supplies into the city for central distribution to other hospitals.
Compare this with Birmingham, where the need for air transport is highly tactical, between locations without airports - helicopters; hub and spoke to a main hospital, better time and distance than road.
Strategic supply still required, thus have a main airport base.