Simon had learned to knock on one side of the house and enter on another
Simon had learned how to enter through the living room doors. He was not allowed to go in that way. But it was a way he could make himself visible when we were in the living room. So whenever I was in the living room and he was outside, it was very likely that within 15 minute,s Simon would come to the terrace door. It is of glass, so first thing he would do is try to look in to see if he could see me. I would pretend to ignore him. Then he would after a time raise himself on his hind legs and start "polishing" the glass in the door until I let him in. But I could not open the door (not allowed by my wife, too much dirt would come into the living room). So what I did was to tell Simon that he should go round the house to the front door. And he did. He did run around the house, before I opened the front door, because he understood that was where I would let him in. Then when I opened the door he would run in.
If I now went back to sitting in the living room, he would come and lie on the doorstep into the living room. After a while, he would go to the front door and want to be let out. And I would let him out. Within 15 minutes from that, there would be one big white forest cat on the terrace, looking through the glass in the terrace door, to see if I was sitting in the living room. And then he would start "polishing" the glass again. This would go on, Simon running in and out of the house, and around the house, until I left the living room, in which case he would follow me in the house.