Mid 80ies and SAC N4 was sent to Imber for FIBUA training (Why...??) with a couple of teams of UKMAMS finest. Got dropped off on the main road and walking into Imber with all our kit when a landrover suddenly appeared. Asked who we were and what we were doing there. He didn't seem impressed to be told we were RAF. Turned out he was an umpire we were wandering along the road which was between two opposing tank groups and there was an attack schedule imminently.
With that, a large bush not too away started it's engine and reversed back at a great rate of knots as the Scorpion recce screen had seen the enemy and were legging it out of the way. The umpire said stand next to any trees and not run around and disappeared as well.
So 12 or so MAMS Commandos stood next to trees and hoped the Chieftain tanks would obey orders and go round them.
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Lyneham 1984/5 TAC/MIN EVAL and some of the intruders are local ATC cadets. One of them was rifle butted in the back of the head after capture. A couple of days in hospital sorted out his concussion.
The guard was court martialled and left not long after. ATC not used again as intruders.....