Quote Originally Posted by Montello View Post
I wonder if there is any case law on what a good reason could be?

Why would you need a long locking blade to walk a dog?

I guess you are unlikely to ever get into trouble for carrying one of these unless you did something stupid.
There may be case law but you are correct, it's left to the appreciation of the officer controlling you, the desk sergeant, the CPS and the judge, if it goes that far.
An opinel 8 or 9 are not a long blade, even though it does exceed the legal length for EDC, as well as having a locking blade. But it's a good working knife should you need to cut anything bigger than a twig, or your dog's collar if stuck in wire.

Interestingly, the law in France is identical in terms of EDC*, yet the attitude is very different (for now; as civility degrades across the Western world I have no doubt that things will get worse unless we try to repair the social fabric) and while you'll get nicked for any sort of zombie knife, or if you behave stunningly with a fruit knife, no gendarme will bat an eyelid if you are just being controlled at random and have one of those 2 knives in your pocket.

*: it differs in as much as switchblades are legal to own for example, but not for EDC