"Tanks reasons" refers to an obscure law dating to 1915 detailing the reasons for National Security on sensitive war projects. As the project of constructing armoured vehicles was of the uttermost secrecy, a law was created stating that any who discussed the vehicles should be shot and then court marshalled, in that order. Unfortunately it was forgotten about in all the hubbub, and it is still technically illegal to discuss tanks in public.
Why did I bother writing that?