The Return of Chav-cat

We came back from Maelstrom to discover Chav-cat mewing on the windowsill. When we moved towards him, he ran away, but his mewing had sounded a bit pathetic, so we tried something. We had, of course, left the kitties with plenty, but we fed them anyway. They ate their fill and wandered off. Then we refilled their dishes and left the kitchen. Less than 5 minutes later, we came back to find both dishes empty. Either he is a total gronfitter, or he was very hungry; the sort of hungry a cat might get if he hadn't eaten for a couple of days.

Now I have never had conclusive proof that Chav-cat is the evil pisser-on-plants whose toxic urine led me to almost burn the house down; there is a vague possibility that Spoilt White Attitudinous Ginger Git (SWAGgit) is the culprit. The latter has tried to beat up the kitties, the former gets on really well with them. He won't come in the kitchen if we are there, but when we aren't, he's in and out as though it's his home. He's eating the moog food, a crime I have always treated as proof of his inherent knavery, and I will happily threaten him with water pistols if that's the case. Oh, for when we can afford the outside catflap.

But suppose he's a stray rather than a sponger?
Suppose this idiot is hanging around because there's nowhere else to go?

The local cat rescue place suggests leaving food out for him next to the shed, so he has shelter, and then putting adverts in the papers to see if his owner comes forward. What am I supposed to say?

FOUND:
One large black cat with small white bib. Eats everything. Pisses everywhere. Hates human beings. Phone Smokingboot on 0155 555 555 to receive details of filthy habits (the cat's not hers). Invoices for neutering cat and professional carpet cleaning available on arrival.

I really want to catch him and get him to a vet, see he's microchipped, but he's elusive. Anyone out there got any ideas on how to catch him, I would really appreciate hearing them.