"I was once on final in a glider with an instructor, at 400 ft he said "I have!" And spun it losing 200 ft. "You have" he said as two Tornadoes roared overhead at 4/500 ft. I recovered it and landed, along with "what the f**k". So it is possible."
If true, I sincerely hope this instructor NEVER flew again, let alone instructed.