Rupert seems determined to steal every single one of Peno's favourite spots...
After much discussion with other cat aficionados, we've come to the conclusion that he must feel safe where ever her scent is. He certainly seems to like her and the fact that they aren't best friends is not his fault. He talks to her a lot, and has no problem getting in her business (but not in a pushy way like Rocky would have.) She's tolerating him for the most part, but has no problem telling him off when he invades her personal space.
Of course, this particular spot is a little bit of a double whammy. It's actually Dave's chair, and it's suppose to be a complete no-cat zone.
I keep trying to tell Dave that no-cat zones don't exist. And besides, doesn't it look that that spot was absolutely made for Ru?