Well, that was a little odd.
I just got in, a little earlier than I have been this week, and he was waiting for me by the front door! That's a little unusual in itself, I think that's only happened once before, normally he'll let himself in via the cat flap around the back.
He came in, and scoffed down some supper, with Zev, who seemed ambivalent about seeing him.
Then he wandered up to the front door, and waited for me to come and let him out, which isn't something I've ever really done. I've let him out very occasionally when I've been going out, but mostly he'll come and go via the cat flap. I wasn't going to open the door, but needed to get something from my pannier (and the bike was by the door), and he became quite aggressive, very unusual for him, growling, and even gave me a small scratch on the arm.
Eventually he got the idea about the cat flap, and left that way. I opened the back door, since neither of them is exactly keen on the cat flap if they can avoid using it. He came back in for a bit, having a brief wander around downstairs, before going back out again. He growled a little at Zev, but neither of them did any paw waving or proper arched back and furry ball of fuzz.
I wonder if he's been in someone's house, where he's been dependent on them letting him in and out of the front door? He's still wearing his collar and tag, so it's not as though someone's taken him in as their pet.
I guess he's been wandering about, getting food where and when he can, and possibly in houses along here, similar to this one, but going in and out via the front door.
I think I'm just going to have to get used to him appearing and disappearing a lot, when the weather's nice and pleasant as it is now.