caught the sketching bug during work

A colleague brought this bicycle to the studio for students to draw. The sketching bug got onto me that I had to sit next to the students and sketch. The young student sitting next to me must have felt so intimidated as he took a very long time to just draw a few lines. I remember talking to myself : "How is he going to finish the drawing with tonal values before the class ends? Oh dear, I better leave now." So I left the class without looking at his face and please if you are that student reading this, I apologise for intruding into your class.