Sir Alastair Cook
Ex-England captain on BBC Radio 5 Sports Extra

Australia would've expected South Africa to come out hard but they have to keep the stumps in play. A lot of the deliveries have been quite shaky.

Jonathan Agnew
BBC Chief Cricket Commentator on Test Match Special

South Africa are picking up these boundaries pretty quickly now. Nothing by playing dangerously, they've just been picking up on everything that they can.

First change for Australia as Pat Cummins brings himself on to replace Mitchell Starc.

Wiaan Mulder knocks him for two behind square but then sees a delivery jag past his bat - no matter, he strikes the final ball of the over for another four through the point region.

Andy Zaltzman
Test Match Special statistician

Aiden Markram scored four centuries in his first 10 Tests but he's averaged 29.73 since then.

Jonathan Agnew
BBC Chief Cricket Commentator on Test Match Special

South Africa have got to be positive and try and put some pressure back onto Australia.

It would be a triumph if they won this. It is a tall order.

Wiaan Mulder gets his turn to face a few deliveries after Aiden Markram dominated the strike in the last couple of overs.

The number three lashes a cut through point for four, the only scoring shot off Josh Hazlewood's six balls.

Vic Marks
Former England spinner on BBC Radio 5 Sports Extra

Not a great delivery from Mitchell Starc again but Aiden Markram middled it.

Jonathan Agnew
BBC Chief Cricket Commentator on Test Match Special

That's what it's all about, putting it back on the bowler. It was a poor delivery from Mitchell Starc but Aiden Markram just putting the pressure back on.

Aiden Markram was bowled for a duck by Mitchell Starc in the first innings, but the opener seems determined to do better on this occasion, striking two fours from the over.

He times a full-ish delivery nicely through cover point, then works one off the legs to find the ropes at backward square.

Image source, Rex Features

Vic Marks
Former England spinner on BBC Radio 5 Sports Extra

The game is still on but that was a big setback for South Africa. Ryan Rickelton can put up a big score but he got out in a strange way.

Vic Marks
Former England spinner on BBC Radio 5 Sports Extra

That's a sweet stroke. I feel like it's easier to bat out there at the moment.

Lovely shot from Aiden Markram, punching Josh Hazlewood's delivery through the covers for four.

The Australian seamer almost has his revenge from the following delivery, beating the bat of South Africa's opener.

Hello to Dave - the man who first published some of my sports writing when I was 13.

A man of sound judgement - and he's right here, of course.

Australia were chasing 282 at Edgbaston in 2005 - they were bowled out for 279, with Michael Kasprowicz controversially given out caught behind off the bowling of Steve Harmison, to give England a famous two-run victory.

Another close finish like that would very fun indeed.

Vic Marks
Former England spinner on BBC Radio 5 Sports Extra

Image source, Getty Images

Mitchell Starc loves to get that ball swinging, especially early on. It's worked so far.