LJ,
The E-3D can change a planned mission with the permission of FC provided that the original mission was a routine training sortie but did not provide the minimum agreed quantity of training for the crew. It may well be that Waddington requested the change to "QRA" from such a sortie. In any event, the permission of FC would have to have been obtained to carry out the tasking (unless, of course, a routine training sortie was planned in the UK that day, and it was held on the ground to meet the Q commitment). It became a quite frequent occurrence for the E-3D to move TACON to the UK if a continental TACON could not provide any aircraft to control.