How a key ring can be an offensive weapon

A British 'entertainer' is currently in court for possessing an offensive weapon. The weapon in question is what he uses as a key ring and is a kubotan: a five inch metal rod developed as a self defence system in your pocket.

The 'entertainer' in question maintains that he wasn't aware of this aspect to what he maintains is simply his way of not losing his keys. I am somewhat intrigued to see how this develops and to see if this is seen as a weapon. Is carrying some offcuts of dowel home from the DIY shop an illegal act? Or indeed a six foot curtain rail in the same form and weight as a bo staff going to cause legal problems?

Admittedly the kubotan is directly advertised as a self defence weapon and as well as being able to be used to strike, and to gain leverage in locks and pins, when keys are attached can be used as a flail. But the kubotan is a development of the traditional 'yawara' weapon used in many martial arts which is simply a short stick. Just as the kubotan was used by police forces in the US in the mid 1970s it seems that the yawara was introduced some 40 years previously to the Californian police force by Professor Frank Matsuyama. Matsuyama's yawara use was seen as 'humane' as it "enables a man to overcome his opponent before trouble can really begin" (ref).

This following video shows a modern take on defence with the kubotan by some krav mga practitioners:

And another showing how effective and somewhat viscous this little stick could be in a self defence situation:

So I can see how these small sticks can be brutally effective but surely the intent has to be to use it as a weapon. Or is this a cop out? After all, if it's classified as a weapon, then there's not much to say in its defence. It'll be interesting to see how this current kubotan court case pans out here.

Can anything be used as a weapon? What about a magazine? Surely not...

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