The previous CAR 1988 compilation (Start Date 01/10/2009) had the following:
166 (2) (g) before landing, descend in a straight line starting at least 500 metres from the threshold of the landing runway and at a distance common to the ordinary course of navigation for the aircraft type; and
I couldn't find any reference to this in the most recent compilation (Start Date 03/06/2010).
ComLaw Management - Series- Civil Aviation Regulations 1988