I did it instinctively.

We are in an concert hall for some concert. I arrive early and grab a prime seat. This elderly woman comes over and grabs a seat 6-7 seats from me. The hall fills up.

The woman leaves to go to the washroom.

This dude grabs her seat.

She comes back and protests, but he would not listen. People complain, but he is not going to budge. His argument: "Seats can not be reserved here"

I eye signal to the dude to come take over my prime seat. I grab my stuff and pretend to be on my way out missing the concert entirely. The lady also thinks I am leaving and everyone will have a seat and be happy.

He quickly starts rushing to my place. The lady sits in the place he vacated.

Oops. I changed my mind. I quickly sit down and enjoy the concert.