I think that everyone is aware of the situation regarding knives and public places. The obvious and sensible option involves contacting whoever you are traveling with before you travel, explain the situation, provide evidence of the trip`s intention if they ask for it, and gain some sort of written confirmation they are aware of what you are carrying and adhere to any and all requests they put forward in how that item is carried while under their responibility.
I have always taken this approach and never had any problems carrying knives and axes through airports, on trains you name it. Be honest and open and should they have a problem, arrange alternate travel for yourself or the item.
As far as the Police are concerned I personally can understand them being all too prepared to confiscate and remove passengers if they feel the item could possibly be a danger to others. At the end of the day, they dont care who, why and what the reasons are for us having a blade, they are simpley working in the interests of public safety.
The responsiblity rests firmly on our shoulders i belive to make sure our trips do not contribute to the concerns many already have that anyone carrying a blade is a nutter of some description. As I said, i have travelled many places and never ever had any problem, in each instance everyone has been made aware of what i`m carrying and the purpose and as i have a ticket in my hand, it has meant they are happy to allow me passage with that item (though obviously always in cargo) so really, with pre-planning, these sorts of things should not happen.