Quite a few years back I was exploring and had a leatherman multi tool with me, to cut a long story short I got searched and they tried doing me for "possession of a bladed object" as it had a locking blade, and they considered going equipped but didn't bother.
you might find this an interesting read, didn't write it myself.......
The CJA 1988 mainly relates to carrying knives in public places, Section 139 being the most important.
"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)]
The phrase "good reason" is intended to allow for "common sense" possession of knives, so that it is legal to carry a knife if there is a bona fide reason to do so. Examples of bona fide reasons which have been accepted include: a knife required for ones trade (e.g. a chefs knife), as part of a national costume (e.g. a sgian dubh), or for religious reasons (e.g. a Sikh Kirpan).
In this case, public place is meant as anywhere accessible to the public, so for example a private campsite, which members of the public must book to use, is a public place. Also, knives should only be carried to and from and used at the location where they are needed. For example, leaving a knife in a car for use when you go fishing would be illegal. It should be taken back into the house each time you use the car (other than to go fishing).
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The special exception which exists in the Criminal Justice Act 1988 (s139) for folding knives (pocket knives) is another "common sense" measure accepting that some small knives are carried for general utility however even a folding pocket knife of less than 3" (76mm) may still be considered an offensive weapon if carried or used for that purpose. It was a long held common belief that a folding knife must be non-locking for this provision to apply.
A Crown Court case (Harris v DPP), ruled (case law). A lock knife for all legal purposes, is the same as a fixed blade knife. A folding pocket knife must be readily foldable at all times.
If it has a mechanism that prevents folding, it's a lock knife (or for legal purposes, a fixed blade) The Court of Appeal (REGINA - v - DESMOND GARCIA DEEGAN 1998) upheld the Harris ruling stating that "folding was held to mean non-locking". No leave to appeal was granted.
