I'm not sure what the law actually is. I think you're not supposed to have anything vicious along anywhere where there's public access, so no razor wire or metal spiked railings. But a string of barbed wire is an acceptable topping for the wire fencing around farmers fields, both alongside roads and public rights of way, and in "right to roam" areas, it's hard to see how they draw the dividing line between that, and barbed wire along your boundary.

I agree that one could argue that deliberately setting barbed wire across a path taken by a trespasser in the dark and not in full possession of his faculties could be viewed differently. But one wonders what would have happened had you, Baz, not accepted the ASBO? Could you have argued your case adequately in court? (assuming sufficient funds, which few of us have).