During my flying instructors course in the RAAF the instructor informed me he was now the "student" and I was let him undertake an 8-turn spin in a Wirraway (looks like a Harvard or SNJ) and its recovery.
After 8 turns I told him to recover but he made no attempt. We had parachutes in those days and I knew if things got serious I could always jump and leave him to it. I again requested him to recover, NOW. He replied over the intercom in a seemingly scared voice that he couldn't recover. I told him that I had control and for him to let go of the controls, SIR.
But he had the controls jammed hard-over in the pro-spin position. I asked him again politely to let go of the controls but he said he was scared. We had lost 5000 ft by now and now I was getting worried. In the end I exploded in anger at his stupidity and IMHO, too much realism.
The student/instructor relationship rapidly deteriorated from then on, as did the military rank difference. I was a young 24 year old sergeant and the instructor was a Flight Lieutenant 35 year old veteran former wartime Spitfire pilot. With the ground getting nearer, I told him in no uncertain terms to "Get your frigging hands off the frigging controls". Except I didn't use, `friggin`.
Immediately, the controls became free and I recovered from the spin with a couple of thousand feet to spare but still too close for my comfort.
At the subsequent de-briefing, I apologized to him for swearing at a senior officer while on duty. He just grinned and said I did exactly the right thing under the circumstances. In other words if all else fails and a student freezes up on the controls, you may have to resort to loud foul language to shock him out of his panicked state. Fortunately I have never had to use that advice.
Many years later the instructor had left the Air Force and became an Anglican Bishop. I wondered if he ever swore at his flock from the pulpit.
