Meant to follow up with this and forgot!
We moved to a new area a few years ago, less urban (but same area - more trees, bigger garden) and there are loads of cats round here. My poor Ginger Boy was so lost without his Naughty Tortie that he eagerly approached any cat who came near him, resulting in him being utterly battered as they're not a friendly bunch here :(
This then impacted on my girl cat, because GB would want to play with her (he's 3 years younger) and she doesn't "do" playing, so they'd then end up fighting. It was a bit of a nightmare.
Anyways I have a very established hedge bordering my front garden on one side. At the end of the hedge is a large tree and bushes. There's a little nook where GB loves to sleep - rain or shine, cool in the summer and warm in the winter. A few other cats have also discovered this spot.
One in particular looks feral. He's quite skinny, but may just be old (can't get close enough to check him over) To begin with they would sit on opposite sides of the garden. Then they moved closer until one day I found them sat, like the sphynx, slow blinking at each other.
Black cat now is a regular caller and is even tolerated by Girl Cat. My two fight less now as well, which is a relief.