Think again:
What You Can't Have ...
The following items are banned from sale within the UK (although if you already own one you may keep it, but not use it outside of your own property) ... Switchblades, automatics or 'flick-knives', gravity knives, balisongs or 'butterfly knives', push daggers, belt buckle knives, sword canes, or knuckle-duster knives.
Late on in 2004, an amendment to the law was introduced which restricts the sale of any knife which is not readily detectable by the normal methods of detection, ie: either x-ray or metal detection, unless it can be proven that the knife's sole purpose is for the preparation of food. So for instance, the Cold Steel CAT Tanto or Lansky Knife are now prohibited within the UK.
You may not buy any knife designed to look like something else, for instance a knife which appears to be a pen, (and it doesn't matter whether the pen works or not, it's still a concealed weapon).
Again I ask, please can you have a discussion without personal remarks or name calling, is that to much to ask?