Bens Stokes and Foakes have since moved England into the lead with the skipper slog-sweeping Simon Harmer for six.
However, whether he is able to repeat that shot with this knee concern remains to be seen.
Video content
Video caption: Stokes slog-sweeps Harmer for sixStokes slog-sweeps Harmer for six
Post update
Anrich Nortje has got both wickets for South Africa today. The second of them came with an absolute beauty to end a gutsy knock from Zak Crawley.
Video content
Video caption: Nortje claims Crawley wicketNortje claims Crawley wicket
Post update
It's been a fascinating first hour this morning. Jonny Bairstow started positively for England but he was the first man out, edging Anrich Nortje to slip one short of a half-century.
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Video caption: 'Perfectly placed!' - Bairstow hits four off Rabada'Perfectly placed!' - Bairstow hits four off Rabada
Video content
Video caption: 'Huge wicket!' - Bairstow falls to Nortje on 49'Huge wicket!' - Bairstow falls to Nortje on 49
Post update
Daniel Norcross
BBC Radio
I think it's the knee he hurt in the Trent Bridge run chase. He's just jarred it. It's a deep concern for his batting, and bowling in the second innings. Has he just popped it?
Eng 173-5
Lead by 22
Oh dear. Stokes is down and holding his knee. He ran a quick single to end the over and he doesn't seem to turn sharply but he pulled up quickly.
It's drinks and the physio will come on to take a look. Worrying for England.
Get Involved
#bbccricket
Dave Foot: Stokes and Foakes must go with confident strokes, not timid pokes.
Not out
Eng 170-5
It pitched in line but it's umpire's call on impact and just sliding down leg.
Close but South Africa lose a review. They've got two left.
Post update
Daniel Norcross
BBC Radio
Simon Harmer liked that appeal. He was bouncing up and down on the spot!
Post update
Vic Marks
Former England spinner on BBC Test Match Special
That's partly because they have three reviews in the bag, and it's Ben Stokes. I think Stokes would be fuming, but it looks like it pitches outside leg.
South Africa review
Eng 170-5
Harmer raps Stokes on the front pad and South Africa go up. It's a big appeal but it dies down quickly.
Despite that, Elgar decides it's worth a review.
Eng 170-5
How did that miss? Ngidi's first ball jags back and cuts Foakes in half. Somehow it didn't bowl the England keeper.
A very good start from the South Africa seamer. A maiden.
Post update
Another bowling change. Nortje is done for the time being and Lungi Ngidi is on for his first bowl of the day.
Eng 170-5
Stokes 13, Foakes 13
An interesting first over from Harmer but it's a fruitful one for England, 11 runs from it.
Post update
Vic Marks
Former England spinner on BBC Test Match Special
It wasn't the worse ball in the world from Simon Harmer - as a member of the off-spinner's union it never is when they slog sweep you!
Eng 170-5
Lead by 19
Harmer v Stokes, you say? It's round one to the England captain!
First ball he faces from the spinner, he's down on one knee and slog-sweeps for six. This is going to be fun.
Video content
Video caption: Stokes slog-sweeps Harmer for sixStokes slog-sweeps Harmer for six
Eng 163-5
It's a gift from Harmer to start. A full toss and Foakes thumps it wide of mid-off for four.
Post update
This could be interesting. Simon Harmer is coming on. What can the off-spinner produce? He'll want to bowl at the left-handed Stokes but it is Foakes on strike for now.
Eng 159-5
Lead by eight
Lovely shot. Ben Stokes gets his front foot out, not quite to the pitch of the ball but uses every bit of his reach to thump a full delivery away through the covers.
The slow outfield means the chasing fielder is kept interested until the last but the ball just wins the race. Four runs.
Post update
Simon Mann
BBC Test Match Special
What an Test match this. The fate of it could even hinge on this Ben Stokes innings. A lead of even 60 might be crucial for England, although would still be a sweaty fourth-innings chase. Right at this moment South Africa, you feel, would like to have a fourth seamer here. The big tall left-armer Marco Jansen was left out in favour of a spinner.
Eng 154-5
Lead by three
England are ahead! It's a streaky shot from Foakes, reaching outside off and getting an inside edge that wrong-foots Verreynne and scuttles away to the boundary.
Live Reporting
Sam Drury
All times stated are UK
Video caption: Stokes slog-sweeps Harmer for sixStokes slog-sweeps Harmer for six Video caption: Nortje claims Crawley wicketNortje claims Crawley wicket Video caption: 'Perfectly placed!' - Bairstow hits four off Rabada'Perfectly placed!' - Bairstow hits four off Rabada Video caption: 'Huge wicket!' - Bairstow falls to Nortje on 49'Huge wicket!' - Bairstow falls to Nortje on 49 
Video caption: Stokes slog-sweeps Harmer for sixStokes slog-sweeps Harmer for six 
Latest PostPost update
Bens Stokes and Foakes have since moved England into the lead with the skipper slog-sweeping Simon Harmer for six.
However, whether he is able to repeat that shot with this knee concern remains to be seen.
Video content
Post update
Anrich Nortje has got both wickets for South Africa today. The second of them came with an absolute beauty to end a gutsy knock from Zak Crawley.
Video content
Post update
It's been a fascinating first hour this morning. Jonny Bairstow started positively for England but he was the first man out, edging Anrich Nortje to slip one short of a half-century.
Video content
Video content
Post update
Daniel Norcross
BBC Radio
I think it's the knee he hurt in the Trent Bridge run chase. He's just jarred it. It's a deep concern for his batting, and bowling in the second innings. Has he just popped it?
Eng 173-5
Lead by 22
Oh dear. Stokes is down and holding his knee. He ran a quick single to end the over and he doesn't seem to turn sharply but he pulled up quickly.
It's drinks and the physio will come on to take a look. Worrying for England.
Get Involved
#bbccricket
Dave Foot: Stokes and Foakes must go with confident strokes, not timid pokes.
Not out
Eng 170-5
It pitched in line but it's umpire's call on impact and just sliding down leg.
Close but South Africa lose a review. They've got two left.
Post update
Daniel Norcross
BBC Radio
Simon Harmer liked that appeal. He was bouncing up and down on the spot!
Post update
Vic Marks
Former England spinner on BBC Test Match Special
That's partly because they have three reviews in the bag, and it's Ben Stokes. I think Stokes would be fuming, but it looks like it pitches outside leg.
South Africa review
Eng 170-5
Harmer raps Stokes on the front pad and South Africa go up. It's a big appeal but it dies down quickly.
Despite that, Elgar decides it's worth a review.
Eng 170-5
How did that miss? Ngidi's first ball jags back and cuts Foakes in half. Somehow it didn't bowl the England keeper.
A very good start from the South Africa seamer. A maiden.
Post update
Another bowling change. Nortje is done for the time being and Lungi Ngidi is on for his first bowl of the day.
Eng 170-5
Stokes 13, Foakes 13
An interesting first over from Harmer but it's a fruitful one for England, 11 runs from it.
Post update
Vic Marks
Former England spinner on BBC Test Match Special
It wasn't the worse ball in the world from Simon Harmer - as a member of the off-spinner's union it never is when they slog sweep you!
Eng 170-5
Lead by 19
Harmer v Stokes, you say? It's round one to the England captain!
First ball he faces from the spinner, he's down on one knee and slog-sweeps for six. This is going to be fun.
Video content
Eng 163-5
It's a gift from Harmer to start. A full toss and Foakes thumps it wide of mid-off for four.
Post update
This could be interesting. Simon Harmer is coming on. What can the off-spinner produce? He'll want to bowl at the left-handed Stokes but it is Foakes on strike for now.
Eng 159-5
Lead by eight
Lovely shot. Ben Stokes gets his front foot out, not quite to the pitch of the ball but uses every bit of his reach to thump a full delivery away through the covers.
The slow outfield means the chasing fielder is kept interested until the last but the ball just wins the race. Four runs.
Post update
Simon Mann
BBC Test Match Special
What an Test match this. The fate of it could even hinge on this Ben Stokes innings. A lead of even 60 might be crucial for England, although would still be a sweaty fourth-innings chase. Right at this moment South Africa, you feel, would like to have a fourth seamer here. The big tall left-armer Marco Jansen was left out in favour of a spinner.
Eng 154-5
Lead by three
England are ahead! It's a streaky shot from Foakes, reaching outside off and getting an inside edge that wrong-foots Verreynne and scuttles away to the boundary.