I worked in a steel mill once when I was just out of college, brown belt in yoseikan aikido. I was teaching a class and all my coworkers knew it. One guy was a good bit older, fat and had a pretty sour attitude a lot of the time. We got on the subject of his military experience and he said he'd been an MP.
I said he probably learned a lot of arresting techniques and asked him to show me one.
For a fat old guy, he moved really fast. He had me in a pinch of my upper lip, just below the nose and I couldn't do jack. I was up on my toes in a very accommodating attitude. He was nice enough to let me go. You would have never thought he knew anything to look at him. Just shows to go you never know who you're dealing with.