….The relevant wording is: “It is an offence for any person, without lawful authority or good reason, to have with him in a public place, any article which has a blade or is sharply pointed except for a folding pocket-knife which has a cutting edge to its blade not exceeding 3 inches.” [CJA 1988 section 139(1)]
Lock knives are not classed as folding knives and are illegal to carry in public without good reason. Lock knives:
- have blades that can be locked and refolded only by pressing a button
- can include multi-tool knives - tools that also contain other devices such as a screwdriver or can opener
….As far as I am aware, this is not based on statute law, and is solely based on case law. I can find no definition of lock knives or their status in statute law.
Indeed, all the guidance I've seen says "non-locking". As you say, it isn't explicitly clear but my understanding is any knife with a locking mechanism is a "lock knife" and not street-legal.