What is this?

I’m not sure if I’m just a dumb Londoner, but is this a ferret? I’ve never come across one before, and was just out on a dog walk and it was very placid (but was beelining straight to a busy dual carriageway!). I managed to lure it back to a hedge with some leftover dog treats, but i’m unsure if it’s a wild animal or someone’s escaped pet… 🙈