> Arrivals and departures suspended at Heathrow? How isn't this a complete overreaction?

The runways and taxiways that planes would normally be using arriving and departing are being used, or may need to be used, without delay by emergency vehicles.

The simplest and safest way to assure that this can be done, and done safely, is to not have aircraft using them for landings, takeoffs, and taxiing.