I'm looking for a technicallity in British law- I'm being railroaded over nonsense- please read on to help me?

Your only defence is if you were on your way to or from work as a previous posted has stated. If you had the blade on you at any other time without a phenomenally good reason, you are in possession of a bladed article in a public place which is a criminal offence. The fact that you didn't get it out in public has no bearing as you were still in possession of it.