The only way I can see that it might not be legal would be if it was an offensive weapon. So, what's an offensive weapon???
The CPS say an offensive weapon is "any article made or adapted for use to cause injury to the person, or intended by the person having it with him for such use".
"It's not made or adapted to cause injury, your honour, it's just a security device so far as I could see. And I only ever thought of it as a security device, it never even crossed my mind that you could hurt somebody with it, I never intended to hurt anybody, on my baby's life."
Case dismissed.