Morne Morkel does his usual turning circle at the top of his mark before he comes in and gets Cook to have an uppish-looking prod at the ball. The bowler shrieks like a man possessed as he strikes Cook on the pad but, nah, that's missing leg. Brilliant work from the SA seamers this morning. Neither batsmen is looking comfortable, Cook falling over in his crease slightly as he searches for his first run.

Stephan Shemilt
BBC Sport at Old Trafford

Poor Keaton Jennings. You know you're under pressure when the crowd cheer the first time you lay bat on ball. Talk about damned with faint praise. When he gets off the mark, there's an eruption of noise.

Seriously athletic work from Rabada to get to that ball. He came racing up to get right under Jennings' nose. The batsman edged it into his thigh and it came popping up at a catchable height. As Aggers said, a short leg would have snaffled that up.

Image source, Getty Images

Jonathan Agnew
BBC cricket correspondent on TMS

A short leg and that would've been out - no problem.

Jennings dropped on 4published at 1.3 overs

1.3 overs

Eng 4-0

This is sensational stuff from Kagiso Rabada. He beats Jennings with a beauty of a delivery first up before Jennings pushes forward to third ball. It takes the inside edge, the ball balloons up, Rabada comes charging forward, just about gets to it - and the ball slips through his hands and into the turf!

Phil Tufnell
Ex-England spinner on BBC Test Match Special

I think there will be seam movement early on. The pitch has a damp look to it - it's not its usual straw colour.

Ooh! Morkel's third ball is a beauty - good length, straight and just beating Cook's tentative prod forward. I'm not entirely sure what Cook's feet were doing there. He looked like he was doing the splits, shuffling really deep into his crease. Quinton de Kock then takes a fine catch, leaping to his right, as Morkel pushes the ball across Cook. Excellent work from Morkel, getting the ball to nip away from Cook's push forward, before beating him for the third time with the last ball of the over.

Morne Morkel removes his sweater - a braver man than I - and strides to his mark. Alastair Cook will face the first ball while Vernon Philander, up in the dressing room, chews thoughtfully on his nails.

Here we go!

Ed Smith
Ex-England batsman on BBC Test Match Special

I felt at The Oval, South Africa were ragged. They had no rhythm to their bowling attack. If they don't get through in this first hour here, this series has taken an interesting twist. I'd back England from here.

Laura Wright, who looks frozen, has just belted out Jerusalem for the crowds as the England openers take to the field. Faf du Plessis and his men are already out there, Faf whirling his arms around like he's ready to take flight.

England have a good record at Old Trafford, having won eight and lost just one of their past 12 Tests at the ground from 2000. However, in the last nine series England have played, they have lost the final Test on eight occasions.

In answer to my earlier query...

Stephan Shemilt
BBC Sport at Old Trafford

WG Grace is much taller than you'd think...

Root might win more tosses but he's got a rubbish technique. Flinging it halfway across the pitch like he's letting a frisbee loose. Cook was much more elegant. No messing around - that coin was up in the air and straight back down in time for the handshake.

Image source, Getty Images

Fenners: Root is already a better captain than Cook based on winning tosses. Win toss, bat first : that's 3-1 then

Phil Tufnell
Ex-England spinner on BBC Test Match Special

Keaton Jennings looks like a sitting duck at the moment. He has to take some chances and if the ball's in his slot, he's got to whack it.

England XI: Cook, Jennings, Westley, Root, Malan, Stokes, Bairstow, Moeen, Roland-Jones, Broad, Anderson.

South Africa XI: Kuhn, Elgar, Amla, Bavuma, Du Plessis, De Kock, De Bruyn, Maharaj, Rabada, Morkel, Olivier.

Ed Smith
Ex-England batsman on BBC Test Match Special

The ball is in Keaton Jennings' court now. It's hard to change your technique mid-series - Graham Thorpe is one of the few batsmen who did it - but he's got to become more fluid and dynamic. At the moment, he's too static. There's a general lack of an ability to melt into the ball and make it look like batting is second nature to him.

So Keaton Jennings keeps his place for Old Trafford - he's not had the happiest of series, scoring just 92 runs in six innings, including ducks at The Oval and Trent Bridge.

The Durham batsman made his highest score of the series - 48 from 78 balls, including nine boundaries - in the second innings at The Oval, and Root has been impressed by Jennings' attitude.

"You speak to him and the way he behaves around the rest of the side, you wouldn't know if he'd come off the back of three hundreds or a couple of low scores," Root said.

"I think that a great way to go about things. The way he has trained and prepared has been very mature, very professional. He's a strong character."

South Africa captain Faf du Plessis: "It looks a pretty good wicket and we'd have batted first. The overhead conditions give us an opportunity. Hopefully the series keeps going the way it has. It's important for us to start really well and get some control of the Test match. Two-all would be great. It's a good test of our character. The previous game didn't go according to plan but w're looking to rectify that."