Caught this guy on Kentish Town platform the other day. He got up and left, but I had enough to carry on shading ( possibly overdoing it a bit )
The Thameslink guard came up to watch, and asked how I could carry on drawing when the guy wasn't there. I told her that he had been sitting on the bench only moments before, and was still in my mind. She asked if I would draw her, which is a fatal thing to agree to, as it then becomes official, and you are then 'performing' and the end result is rarely any good. I politely ( I hope ) made up an excuse that I wanted to finish this one. She wandered off, then sat in the exact seat this guy had been sitting in, as if that would somehow trigger me into sketching her. And that part of me that wants to make people happy so wanted to, but I have been once bitten that way too often before.
Lynne Chapman has some great advice on the rules and don'ts of sketching people in public over here.
Eventually the Guard wandered off, and I did an appalling sketch of the guy on the opposite platform, appaling. Serves me right.