This is Patch. He's a young black and white tom who 'visits'. We don't know his real name or where he lives - but he visits regularly - and is tolerated by Vel and Arty. He is very vocal and affectionate, and obviously not a stray. However he always finishes any food that's left in their bowls and will miaow loudly if there isn't any.
He also has a magnetic collar so he gets in via the 'clever' catflap. I often wonder if our cats go home with him sometimes!