ExSimGuy - suggest you read the inside of your ticket more carefully (as should all passengers, but it does seem they can't be bothered).
All airlines have a section after the contract of carriage in regard to Dangerous Goods In Passenger Baggage - BA even have it on the back of their boarding passes now as well.
This section details what you should not put in any baggage that you will check-in.
GF does supply its agents with similar placards for the check in desk - however you will rarely see them in BAH for some unknown reason.