Apparently it's just been made law that it's compulsory to microchip all cats.

[Silverlog]

I've always microchipped my cats and as far as I'm aware, most people do. I've never met someone who didn't microchip their cat. We risk a £500 fine for not complying.

My grandma had a next door neighbour who had 2 cats, one of whom was as dull, boring and unadventurous as the neighbour and spent all day on the windowsill napping, and the other of whom was intelligent and adventurous and playful, and frankly preferred the company of my grandma rather than his "official" owner and spent most of the time around at her house rather than at his official home, if he wasn't out in the gardens exploring. No one gets to tell a cat who they belong to. I doubt this law is genuinely enforceable because the absence of a chip simply means that no one is going to take responsibility for being a decent cat-slave, it will be easy enough for anyone who doesn't chip their cat to just claim that the beast just hangs around their house but isn't really theirs.

Dodgy breeders will just get their own chips & diy.