For, in every sense of the word, this is life on the edge. Come rain, wind or shine, the tours go ahead. Every kind of weather buffets you up there on the top of the world. But climbs are stopped in electrical storms. They also called a halt when 50 knot gusts hit Sydney in the run up to the Olympics and caused travel chaos with fallen overhead train wires.
Safety is paramount on the slickly packaged three-hour tour.
It begins in the hangar-like reception where visitors are briefed and, for what is already a very sobering prospect, breathalysed. Empty your pockets, take off all watches and bracelets to avoid them getting caught on the rails as you climb. Clip on sunhat, sunglass cord and rain hat if the elements are going to turn against you. No cameras are allowed in case you inadvertently bombard the traffic below. First comes a quick rehearsal on the bridge mock-up before you step out onto the lower reaches of the bridge.