The good news for England fans is that Stokes is going to continue - and he seems to be moving pretty well.

One to keep an eye on but, for now at least, it doesn't seem to be as bad as it initially appeared.

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.

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.

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.

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?

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.

Dave Foot: Stokes and Foakes must go with confident strokes, not timid pokes.

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.

Daniel Norcross
BBC Radio

Simon Harmer liked that appeal. He was bouncing up and down on the spot!

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.

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.

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.

Another bowling change. Nortje is done for the time being and Lungi Ngidi is on for his first bowl of the day.

An interesting first over from Harmer but it's a fruitful one for England, 11 runs from it.

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 170-5published at 39.4 overs

39.4 overs

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.

It's a gift from Harmer to start. A full toss and Foakes thumps it wide of mid-off for four.

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.

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.

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.