ABSOLUTELY AND DEFINATELY UNLAWFUL TO POSSESS IN A PUBLIC PLACE IN THE UK!
I can think of no "lawful authority or reasonable excuse" to be in possession of one of those outside your place of abode and, in fact, it is specified to be an "Offensive Weapon." See (e) below.
Interestingly, some wag on eBay was selling similar knives described as a "letter openers" but slightly smaller and made of a polycarbonate material so as to make them invisible to X-ray and metal detectors! (see (p) below) I think it must've been reported to eBay pretty quick, because between me seeing it and making a cup of tea, the listing had vanished.
THE LAW!
1. Section 141 of the Criminal Justice Act 1988 (offensive weapons) shall apply to the following descriptions of weapons, other than weapons of those descriptions which are antiques for the purposes of this Schedule: (an antique is a weapon more than 100 years old)
(a) a knuckleduster, that is, a band of metal or other hard material worn on one or more fingers, and designed to cause injury, and any weapon incorporating a knuckleduster;
(b) a swordstick, that is, a hollow walking-stick or cane containing a blade which may be used as a sword;
(c) the weapon sometimes known as a "handclaw" , being a band of metal or other hard material from which a number of sharp spikes protrude, and worn around the hand;
(d) the weapon sometimes known as a "belt buckle knife" , being a buckle which incorporates or conceals a knife;
(e) the weapon sometimes known as a "push dagger" , being a knife the handle of which fits within a clenched fist and the blade of which protrudes from between two fingers;
(f) the weapon sometimes known as a "hollow kubotan" , being a cylindrical container containing a number of sharp spikes;
(g) the weapon sometimes known as a "footclaw" , being a bar of metal or other hard material from which a number of sharp spikes protrude, and worn strapped to the foot;
(h) the weapon sometimes known as a "shuriken" , "shaken" or "death star" , being a hard non-flexible plate having three or more sharp radiating points and designed to be thrown;
(i) the weapon sometimes known as a "balisong" or "butterfly knife" , being a blade enclosed by its handle, which is designed to split down the middle, without the operation of a spring or other mechanical means, to reveal the blade;
(j) the weapon sometimes known as a "telescopic truncheon" , being a truncheon which extends automatically by hand pressure applied to a button, spring or other device in or attached to its handle;
(k) the weapon sometimes known as a "blowpipe" or "blow gun" , being a hollow tube out of which hard pellets or darts are shot by the use of breath;
(l) the weapon sometimes known as a "kusari gama" , being a length of rope, cord, wire or chain fastened at one end to a sickle;
(m) the weapon sometimes known as a "kyoketsu shoge" , being a length of rope, cord, wire or chain fastened at one end to a hooked knife;
(n) the weapon sometimes known as a "manrikigusari" or "kusari" , being a length of rope, cord, wire or chain fastened at each end to a hard weight or hand grip;
(o) a disguised knife, that is any knife which has a concealed blade or concealed sharp point and is designed to appear to be an everyday object of a kind commonly carried on the person or in a handbag, briefcase, or other hand luggage (such as a comb, brush, writing instrument, cigarette lighter, key, lipstick or telephone).
(p) a stealth knife, that is a knife or spike, which has a blade, or sharp point, made from a material that is not readily detectable by apparatus used for detecting metal and which is not designed for domestic use or for use in the processing, preparation or consumption of food or as a toy;
(q) a straight, side-handled or friction-lock truncheon (sometimes known as a baton)."
Hope this makes the situation as clear as a very clear thing indeed!
