Australia maintain grip

The tourists then poured more misery on their hosts with Phillip Hughes and Simon Katich putting on a half-century stand in quick time to help their side reach lunch at 91 for one.

Katich though, was eventually dismissed for 30, but Hughes (43 not out) and Ricky Ponting (17 not out) helped the visitors extend their overall lead to 305 at the break.

But there was no doubt who the hero was for the Australians, with Siddle following on the good work done by Mitchell Johnson and Andrew McDonald - the pair had each claimed three wickets - on day two that left the Proteas reeling at 138 for seven.

The Victoria paceman struck with just the second delivery of the morning when he tempted Dale Steyn to chase a wide delivery that took the toe end of the bat through to Brad Haddin for eight.

It was a crucial blow to the South Africans, especially after Steyn showed incredible concentration in his hour long stay yesterday to help JP Duminy move to within 17 runs of his century.

And his dismissal was followed up with that of Makhaya Ntini the very next delivery when Siddle's angled delivery trapped him in front for a duck, leaving Duminy unbeaten on 73 and having not faced a ball on day three.

The South Africans were also left 15 runs short of avoiding the follow on, but Ponting opted not to reinsert them.

Instead, the tourists came out on a mission with Katich and Hughes raising the 50 stand in just 66 balls, before the former tried to angle a Jacques Kallis delivery down to third man, but was excellently snapped up by AB de Villiers at gully for 30.

But Ponting and Hughes continued the Australian march leaving them well placed at lunch.