If you try to cut someone with the knife blade, you'll likely end up breaking it off or closing it on your own fingers. A knife weapon absolutely needs to have a fixed or locking blade.
And that's why a police officer will never have a problem with a non-locking pocketknife. A cop might. A pig definitely will. As long as the latter exist, you might as well carry a tool-knife with a "legitimate purpose" that can also be used as a weapon-knife if necessary, because following the spirit of the law won't help you it a letter-of-the-law bastard gets it in his head to screw you over.
https://en.wikipedia.org/wiki/Fatal_dog_attacks_in_England_a...
This whole thing is just nonsense and another form of humiliation of the oppressed by "the" "state".
It's almost as if this is an incredibly minor consideration.
If you've gone to a bar after your dinner party, and you're carrying the "cooking" knife somewhere accessible (like your pocket), that could be a problem for you.
Children in rough areas should interpret the rules less favourably.