Many years ago when I was in England, there was so much smog that you had to use instruments to fly a circuit, and one day the parachuting was discontinued as visibility was not good enough. Nil cloud, poor vis. The local flying instructor told us that "if you can see the ground you know which way is down, so you should be able to fly." The tower had a VHF direction finder, and could help aircraft get home. (Strange that Australian towers do not have it)