Squidders said:
Carrying your knife to work because that's where you need it is not a good excuse because they can just ask why you don't leave it there. and any high value you put on the blade is no real argument as people leave laptops at work
Correct, that reason only works while you're at work. You could probably sucessfully argue a simple and direct transport to and from work with the knife is reasonable, but I wouldn't bank on it. If you need it for work, and you dont work weekends, you have no reason for having it at weekends.
Squidders said:
Most locking blades clip open when you pull the blade out and you have to push/pull something to unlock it... I was thinking about opinel blades... they require an action to lock the blade in the first place... technically, by jamming something in any non locking knife you have a locking knife... is there a diference? and what's legal?
An opinel is a locking knife. You need a reasonable reason to carry one, just as you would if it were a sheath knife.
Jamming a folder open, would probably constitute modification of the knife - just like welding it open would. However, the knife itself, is not illegal before you jam it open. The law says "it must be readily foldable at all times" - if you do something to jam it open, it stops being readily foldable and you've turned it into a knife that is potentially illegal (you'd need a reason to have it).
There is no way round this, there is no get out. If it locks, you need a reason to carry it, or you are breaking the law. An officer may disagree with your reason and arrest you anyway, that is his right. You may have to prove your reason in court. The court may disagree that your reason is "reasonable" and fine you or send you to prison. So, be sure your "reasonable reason" is indeed a reasonable reason, and not some half baked excuse that you think lamely gets you round the law - it wont!
Using your opinel for bushcraft is a reasonable reason for having it, but only while you are actually doing bushcraft. Using your opinel for bushcraft, is not a reasonable reason for having it with you in Tesco's on a saturday afternoon.