This surprisingly happened to me today. It seemed to have been done accidentally, but if my opponent knew that I had felt pressure, he could have went forth in the correct angle and gotten me tapped! Ok, I was almost in back mount; we were side by side but slanted[Does not matter. Will work in back mount too. I went forth and encircled his neck with my right arm. However, he got hold of my left which was about to finish the choke[ LegHooks not in yet but does not matter] Both of his hand held tightly to my arm onto his stomach or chest[2 arm v 1, he wins]. So my left upper arm was on his left shoulder and neck. For a moment he pushed back upwards[towards where both our heads were pointing. There was the armbar. If he pushed upwards more forcefully and maintained it there, I would hav tapped. He was almost on me then and obviously with his full weight on me[so I had to carry 2 weights, my own n his] and that he has his legs on the floor, only he can move. Wow. You all shld try it. Let me patent this move as thecas armbar ... popularise it.