Birthday boy James Anderson to bowl the last over of the day - can he celebrate another wicket before the close? He goes round the wicket to Elgar, who takes one hand off the bat as he runs a single to square leg. Considering what he's been through today, I wouldn't expect he'd want to leave the non-striker's crease after this... Four balls left in the day.

Image source, Getty Images

If Broad can get through this over in less than five minutes, there will be one more. If he can't, this will be the last one. And there will be those who wonder why we can't carry on, given that (theoretically) there are still three more overs to be bowled tonight, and the light is fine for now.

"He's big, he's bad, he's better than his dad," sing the Barmy Army in appreciation of Broad, but Bavuma - roughly a foot shorter than Broad - sees out the over unscathed, and there's just time for one more.

Graeme Smith
Ex-South Africa captain on BBC Test Match Special

If South Africa could bat out tomorrow it would be remarkable but you just don't feel it at the moment, you feel like defeat is inevitable.

James Anderson, 35 today, is recalled to the attack - much to the delight of a blonde Lancashire fan holding up a birthday banner saluting the "Burnley Lara". Dean Elgar, though, is determined to still be there tomorrow, picking off a two but generally concentrating on defence.

Meanwhile, Bavuma takes his pad off between overs, which wastes a bit of time. Umpire Joel Wilson tells him to get on with it.

Image source, Getty Images

Graeme Smith
Ex-South Africa captain on BBC Test Match Special

The South African bowling attack was always going to test England, it was the batting that was going to be concern. To be all out for under 200 in the first innings, you've got to start asking some questions.

It looks like Joe Root's planning a bowling change, and James Anderson is limbering up for one last spell as Broad continues at the Pavilion End. Bavuma defends well, adding a two to his score - time for three more overs tonight if England don't dawdle? Or two if they spend a while setting the field and generally vacillating?

Graeme Smith
Ex-South Africa captain on BBC Test Match Special

It's certainly been a fighting innings from Elgar, I don't think there has been one ball where he has looked comfortable. It's a good example to youngsters though that sometimes you have to do the hard yards, it doesn't always fly off the middle of the bat.

Moeen now has a short leg and two slips in for the left-handed Elgar - the slips in question being Stokes and Anderson. Meanwhile, it's all been a very long day for a young chap in a dark baseball cap, who is nodding off on his mother's shoulder. Not much turn for Moeen, and a rank long-hop is despatched for four via the covers - scattering a few pigeons as it goes.

Image source, PA

Andrew Samson
BBC Test Match Special statistician

Only three teams have started the fifth day with four wickets down and drawn the Test. They are England against South Africa in 1995 and against New Zealand in 2013. South Africa also did it - in 2013 against Australia in Adelaide. No team has achieved it by starting the day five wickets down.

Graeme Smith
Ex-South Africa captain on BBC Test Match Special

You feel these two have to survive tonight and definitely do one whole session tomorrow at least.

Broad has three orthodox slips and a fifth slip in place for Bavuma, but the little man sees out another maiden over. The Barmy Army trumpeter - and a few South Africa fans - still have plenty left in their lungs as we enter the final 20 minutes of the day.

Graeme Smith
Ex-South Africa captain on BBC Test Match Special

South Africa needed to be no more than two down tonight. They have been very defensive, which has caused two dismissals - Hashim Amla pulling the bat away and Faf du Plessis not playing a shot. I think De Kock is batting too high too. Perhaps shuffle Temba Bavuma up and drop him down to six. At the moment, he's at least one position too high at four.

50 partnershippublished at 18:39 British Summer Time 30 July 2017

18:39 BST 30 July 2017

SA 107-4

Elgar works a two off his legs... then rides his luck as he edges over the solitary slip for four, and Moeen then spins one past his outside edge. But fortune favours the bold - and Elgar now has 65 from 97 balls.

Graeme Smith
Ex-South Africa captain on BBC Test Match Special

You can't think of the task ahead, if you're thinking about still batting at tea tomorrow you're going to make mistakes. You want to stay in the moment, it's a cliche in sport, but you have to stay focused.

A tempting over from Broad, but Elgar remains this innings' immovable object... although hearts are in mouths when he plays and misses with a back-foot prod. Just a single off the over.

Andrew Samson
BBC Test Match Special statistician

On Faf du Plessis' debut, South Africa batted for 148 overs and Du Plessis made 110 not out. They lost eight wickets and saved the game.

They're going to need a similar innings from Elgar and/or Bavuma tomorrow to save this Test.

SA 100-4published at 18:33 British Summer Time 30 July 2017

18:33 BST 30 July 2017

28 minutes of play left tonight - then 98 overs tomorrow

Just over half-an-hour left as England persist with Moeen Ali, despite the TMS team's suggestion of returning to birthday boy Anderson. With plenty of runs still in the bank, England can afford to keep the catching men in place for a long while yet. A juicy full toss is clanged by Bavuma straight into the right shin of Dawid Malan at silly point - these days, close fielders wear pretty much the same leg guards as wicketkeepers (albeit under their trousers) so it shouldn't sting for too long.

Phil Tufnell
Ex-England spinner on BBC Test Match Special

Seeing Alastair Cook fielding in the outfield and not at slip is like seeing a newscaster walking around.

Dave Wood: Proper backs to the wall fighting knock that from Elgar. South Africa dressing room take note.

Image source, Rex Features