"and just how big is a 12 minute circuit"
I suspect its not 'a' 12 minute circuit. More like 5 circuits in an hour from walk out to walk in, probably 2 to roll, 1 to land (taxi round to unscramble Bloggs' brains and give him another shottie at the Take Off Checks), then 1 to roll, 1 to land, and mine's with milk and two sugars.
Terrible shame if the entire AEF and VGS network is to be grounded for a while. But if its in the name of improving safety, who can argue.