Hands up, this is totally my fault!
Being cat lovers, we're always friendly to any cats we see. Last summer when we moved here we didn't have cats of our own but a neighbourhood tom (a scrumptious black and white) would visit us. In the summer, the patio doors were open a lot of the time and he would occasionally come into the house. We never gave him food but we also didn't discourage him from coming in.
Nine months on and we now have our two rescue girls but scrumptious black and white boy still thinks the garden - and, more worryingly, the house - is his. He often comes right up to the patio doors and if either of the girls see him there's a screaming match through the window, usually with Drum who's the dominant cat, although Bass is often around too. They both get upset and I'm convinced it's why Bass won't come into the living room very much.
I don't suppose there's much I can do, is there? I chase him off whenever he gets close but it doesn't stop him and I'm worried that he approaches the window during the day when I'm not around.