I keep telling you you're too polite. A person deserves only the courtesy they extend to others... and a person who interrupts someone else's peaceful, non-intrusive activity, particularly uninvited, is being only marginally less rude than if he or she was unilaterally "sharing" bodily fluids. As such, the most courtesy they are entitled to is a shouted "GO AWAY, MORON!" If that doesn't work, escalation is warranted - maiming may be excessive (or maybe not), but a convincing scream followed by loud accusation of harassment are about right (and, if you keep it to that, actually truthful).

I've had a few people like this recently, yammering at me while I was trying to read on my breaks, and I've stopped trying to be even as diplomatic as I usually am. A pointed, simmering glare, just short of homicidal and held until the target stammers to a stop, followed by a statement along the lines of "I am not interested in you or anything you have to say. Now shut up and leave me alone, idiot" drives the point home nicely - not to the idiot in question, who is almost never smart enough to understand that they aren't the center of my universe, but to anyone else around. The bystanders will usually get rid of the idiots - the bystanders don't seem to want to get splashed if and when I finally lose my patience with the idiots.

You are right. I have to work at being impolite. Twas trained into me. Conditioning. But I am getting there.

K

Sometimes I wish a cute girl would interrupt my reading, but no...

;-)

For everyone else, I find that rudeness works just fine...

Let the annoyer talk for a couple of minutes, without doing anything to acknowledge that he/she's there. Look up at them and say 'Did you say something', then go back to reading.

The fact that you didn't acknowledge the talker for so long can be considered a 'gentle hint' to shut up and leave you alone.
The 'did you say something' is a 'less subtle' hint that you're not interested.

After that it's really OK to tell someone to bugger off.

Giving people a yes or a nod when they ask if they can sit at your table is NOT the same as saying that you're interested in a conversation.