Well, what a strange session that was.

After over an hour of grit, toil and skill by Australia's frontline bowlers, Wiaan Mulder (29) was sent packing with a legside strangulation and Kyle Verreynne (1) was dismissed with the first ball of Matt Renshaw's spell in the very next over.

South Africa still 255 runs behind at lunch, Australia four wickets from victory.

How long will it be until the Durban gloom descends?

This will likely be the final over before lunch.

Nathan Lyon to bowl it.

Markram is defending and taking plenty of time between deliveries, ensuring there isn't any time for another set before the break.

Markram is watching the ball well, on the back foot and dead batting once more.

One ball to go.

And the South African defends off his pads.

That's lunch.

Renshaw is offering plenty of width and Markram is leaving it alone.

The part timer is then presenting a quicker one outside off, which Markram is also having nothing to do with.

Four! Renshaw goes around the wicket and something goes horribly wrong in his release. He provides Jansen a juicy full toss and the South African swats a boundary down the ground.

He is a part timer, after all.

Spin from both ends now for the Australians.

Markram is on the back foot and shovelling a single to long on.

Shout! Jansen is playing and missing outside off and the Australians are up! The ball passed very close to Jansen's bat but there's no serious discussion of sending the decision upstairs.

Matt "Golden Arm" Renshaw continues his spell, and Marco Jansen is padding up well outside off.

Close! The ball collects a mixture of bat and pad and it falls safe of the man underneath the helmet on the off-side.

Jansen is not looking comfortable out there at all right now, but he survives the Renshaw over.

Jansen is working a single to begin the over before Markram is solid as ever with his forward defence.

Slightly too straight from Hazlewood and Markram is turning it away off his pads, earning a single behind square. It's called a leg bye.

Jansen is squirting one into the leg side with the inside edge of his bat and the batters run a single.

Markram is defending to end the over.

Matt Renshaw has five balls remaining in his over. Jansen is watchful to begin before working a single through the off-side.

Drift and turn! There's a puff of dust from the surface as the ball rears back towards Markram, who's defending with a mixture of body and bat.

Matt Renshaw is brought back into the attack and strikes with his first ball!

Kyle Verreynne is dangling his bat out wide and edging through to Steve Smith at slip!

It's a good low catch from the Australian vice-captain.

Verreynne is out for 1, Renshaw has his second Test wicket and the Australians are four wickets from victory.

Well, Australia finally has its breakthrough.

It's wicketkeeper Kyle Verreynne who makes his way to the middle.

He works a single from the final ball of the Hazlewood over.

It's a legside strangulation for Wiaan Mulder, and it's a very good catch from Alex Carey.

The diving wicketkeeper secured the grab with the very top of his outstretched glove.

(Supplied: Fox Cricket)

Mulder throws his head back as he walks off for a 110-ball 29.

Mulder is defending into the off side and then deflecting behind square.

There's a slip, leg slip and short leg in place as Mulder is defending again.

Lyon goes around the wicket to end the over, but Mulder is once again solid.

Starc fires down a bouncer from around the wicket, and Markram does well to get out of its way.

Full and straight from Starc and Markram is solid in defending the ball back to the bowler.

Lyon is coming from over the wicket and has a short leg, bat pad and slip to work with.

Markram is forward and smothering the first ball of the over.

The man underneath the helmet on the off-side moves to leg slip.

Markram deflects one forward of point and the batters scamper through for the first run of the set.

Another dot to end the over.

Starc is dangling a couple out wide and Markram is more than happy to watch them through to Carey.

He then gets one on the pads and turns it behind square for a single.

Lyon again is accurate and Mulder is pushing to mid-on for no run, before defending off the back foot.

The batters swap singles before Lyon comes from around the wicket for the final ball of the set.

It's slightly quicker, full, and Mulder is keeping it out.

Pat Cummins's excellent spell comes to an end, and here he is. For the second time today, it's Mitchell Starc.

He begins with a wild one from over the wicket and changes the angle right away.

Mulder is shouldering arms outside off.

Starc has two slips, a gully and a fine leg slip to work with.

Mulder is patting one into the leg-side for no run.

A quick single to end the over.

Nathan Lyon is pitching a couple good ones outside off. Markram is driving for no run and then defending.

Unbelievable knock so far from Markram. Best known as a white ball destroyer, he has looked as composed as anything during in 165-ball 63.

He's defending again to end the over.