I bet you were worried, the little horror!
As he's been feral for quite a while, I expect his old habits and territorial defending etc haven't entirely left him and occasionally he has a roam. Once he's been neutered he may be more inclined to stay at home.
We got a free sachet of catfood from Tesco through the post, and tried it on our two. They loved it, so we looked for it on the shelves when we were in Tesco's this morning. Of course, it's quite expensive. We only bought four sachets, and we'll see how it goes. Tesco's are naughty, they know how to hook people in!