PC – What is your valid reason for carrying that kind of knife on a bike ride?
Mountain Biker – It’s for cutting cake?
PC – You’re nicked mate….
Little sis, the lawyer advises – The reason must be valid. extremely valid. Blade length will be irrelevant by the time it gets to her. Even if it’s “legal” it can still be an offensive weapon. And it will be a police officer that will decide.
For example if you buy a knife in a shop you must take it straight home. If you go via another shop, you no longer have a valid reason for carrying it. In real life you would think some common sense applies but obviously lawyers have dealt with such cases.