All this excitement is getting too much for me so I need a cuppa to regain my composure. Thankfully, a man who is always cool under pressure is Stephan Shemilt and he will talk you through the the next phase of play.

Geoff Lemon
BBC Test Match Special commentator

It's flatter and quicker from Shamsi. Labuschagne just gets his bat down, but he's certainly been lucky this game. He's playing off the back foot frequently.

Firdose Moonda
Cricinfo writer on BBC Test Match Special

Another 30 or 40 runs from South Africa's innings would be making everyone feel more comfortable now. I think 240-250 may have given South Africa more to work with.

The win predictor has Australia at 90% but watching Keshav Maharaj spinning his web it might be closer than that.

Marnus Labuschagne, however, sweeps the final ball of the over for four to release some of that tension.

Firdose Moonda
Cricinfo writer on BBC Test Match Special

A little bit of an argument there from Steve Smith with his partner between overs. I think Marnus Labuschagne wanted to run but Smith said no.

Tom, Folkestone

Jonathan Agnew
BBC cricket correspondent on Test Match Special

Image source, Reuters

South Africa have got to put some pressure on here. They've got to try and get them to hit the ball in the air. You can only win the match by getting them all out.

The match may well be decided by this battle. Tabraiz Shamsi and Keshav Maharaj versus Steve Smith and Marnus Labuschagne.

Shamsi gives it a bit of air but Labuschagne meets it and drills a rare boundary through the covers.

It feels tense.

Geoff Lemon
BBC Test Match Special commentator

It's tightened right up again. It looks attainable for Australia but the way South Africa are bowling at the moment, it may be close.

Andrew, Hants

Firdose Moonda
Cricinfo writer on BBC Test Match Special

The bowling from Keshav Maharaj is certainly a positive that South Africa can take away from this game.

An absolute peach from Keshav Maharaj, who pitches it on middle and spins to off past Marnus Labuschagne's bat.

Labuschagne breathes a sigh of relief.

Temba Bavuma responds by putting fielders round the bat for the remainder of the over in an attempt to cramp the Aussie batter for room.

Geoff Lemon
BBC Test Match Special commentator

Little edge away from Smith. De Kock is down on one knee. Technically, it's another missed chance from South Africa.

Close!

Steve Smith prods at Tabraiz Shamsi and the ball deflects up off the shoulder of the bat. It hits Quinton de Kock on the body and he is unable to react quickly enough to clutch it into his chest.

It was an incident-packed innings from Travis Head a little earlier as he helped get Australia off to a flyer

Firdose Moonda
Cricinfo writer on BBC Test Match Special

South Africa with a huge task on their hands. It's been good to see how the spinners have gone about it here and they've certainly been unlucky.

Jonathan Agnew
BBC cricket correspondent on Test Match Special

Australia did bowl magnificently. If South Africa lose today, they have been fairly beaten. People shouldn't joke that they have 'choked it'. They will be beaten fair and square by the team on the day.

Keshav Maharaj with the first over after drinks.

A single apiece for Marnus Labuschagne and Steve Smith from it. Almost certainly they will be artisans rather than artists with regards to this chase.

Chris, London

Firdose Moonda
Cricinfo writer on BBC Test Match Special

Shamsi had the same problem against Virat Kohli as he is having here - bowling too many wides down the leg side.

Phew, it's been a breathless 16 overs.

Time to open the drinks cabinet. Make mine a double.