In addition to the Official Secrets Act and need to know principles you learn to keep your mouth shut at times of the year in Canberra. Like in summer when bits of plant or animal float, hover or fly and are small enough to be inhaled if you're riding. I hit a cloud of gnats then went lips shut for the next few kays until I was clear of the places where swarms of gnats live. Later I saw one of those Cottonwood tree balls floating along, like a sky mine ready to choke anyone not applying lip closed sensibility. Canberra: they don't warn you about the inhaling of floating things. There should be a disclaimer.