Used to do that run regularly in my Mini.
(In the ‘sixties, when the Mini was built by BMC, and a proper minimalist, fun car to drive.)
The problem with the run down into Adelaide, if you use the brakes in a heavy vehicle at all, and get caught by one of a million cameras on the way down, it is an immediate fine and loss of points for not maintaining a safe speed ..... they consider a "Safe Speed" means a gear low enough to hold the speed without the brakes being applied .... crazy I know, but never let it be said that the powers that be here in South Australia, particularly near Adelaide, think rationally. There have been so many major accidents involving run away trucks down that section of the hill, they are over the top as far as policing the speed and safety part .....