I said it 15 years ago and I'll say it again; we are running out of runways.
The number of runways required is in proportion to the number of aircraft airborne and their diversion range. It is not proportional to the number of aircraft in the inventory.
Come 1700 there are precious few military runways during the week and at weekends only a couple. As someone once said; the first F3 that diverts to Manchester on a fuel priority will be the last.