If he disbelieves you, explain that the word fork has been outlawed, and saying it might make mummy and daddy have to go away to prison. He wouldn’t want mummy and daddy to go away, now would he?

Make sure you keep this up at all times when he is with you. If a friend or family member happens to use the word fork wait for them to leave and then enact a heated debate as to whether to phone the police or not. If he chooses to grass them up, then make sure he never meets them again.

At some point, you may need to tell him that this has all been an elaborate ruse. Break the news gently by offering him cutlery. If he asks for a bundebangle, tell him you won’t abide such foul manners and leave the house, never to return. Hopefully by this point he will be old enough and wise enough to look after himself, except on first dates, company Christmas meals or similar minor restaurant based situations.

Hope this works out for you, let us know how you get on.