Overly Talkative Student

I need to read about 100 pages of developmental psychology before tomorrow AM, but I have to stay on campus because of a late afternoon lecture. So I find a quiet spot outside and try to get some reading done before my class. Almost immediately I'm accosted by Overly Talkative Student. OTS was a student in one of my discussions last quarter. He talked so much that it became a problem in discussion because other students were giggling every time he spoke. Frequently he kept me talking after discussion for 15-30 minutes and would walk with me to my car, continuing to talk. So my last hour was a complete waste of time. I tried to disentangle myself, but he just won't take a hint. Now I know why professors hide in their offices with the doors locked!