years ago we had trouble with a cat deciding it could come in our house and pee every where, many times. in the end i put the catflap on 'in but not out' closed every door in the house. when i got home i got a rolled up newspaper and chased and whacked the cat up and down the stairs for a minute. ( before all you liberals and animal lovers moan, i didn't do it hard just enough to scare it & decide not to come in our house again. ) then opened the front door, whoosh!!!! one cat that never ventured in again. it was only after he'd peed a few times that i had to do this, so if your visitor doesn't return then no need to chase / scare him.