This one I was there for (well, nearly, about a week later when they were still all talking about it).
Circa 1991, at a helicopter manufacturer's airfield somewhere in SW England - a won't name them to preserve anonymity.
Exercise of the day was IGE hover. The way this was done was by mounting an instrumentation boom on the fire section's landrover, and driving it across the airfield. That established the speed / conditions, and the helo (a Merlin) hovered stationary on the vehicle.
So, picture the scene. The helicopter was hovering backwards IGE, which means that it was leading the landrover. In the ground vehicle you had two FTEs, one watching the instrumentation, one watching the helicopter.
When the helicopter got to the edge of the airfield, it continued over the hedge and to the other side of the road. The landrover, also continued, through the hedge, over the road, through the hedge the other side and came to rest in the ditch.
Since it was the airfield's primary emergency vehicle, not to mention a certain grumpiness over bending their brand new landrover, the fire section were, I believe, rather slow and unhelpful about recovering it.
G