Their styles are quite different, but you can see some similarities between Compton and Jonathan Trott. Both quite intense, both bat in their own bubble. He's warming to his task now, Compton, first getting a controlled edge through the slips for four, then following that up by clipping Morkel off his toes for four more.

Chris Davies: Whatever your Cook can do our Cook can do better. Early prediction - 150 for Alastair.

There are grassy banks around much of Centurion Park. About half the ground, I reckon. It makes for a lovely place to watch the cricket. Lie back on the turf in the sunshine. Probably not so good when it rains. Are there any grounds in the UK with grass banks like that? Abbott to Cook. Straight bowling, straight bat. A maiden.

Former team-mate Mark Simmons tells BBC Radio Berkshire how Stephen Cook, who scored a century on South Africa debut yesterday, made a big impression playing for Reading a decade ago.

Compton is not the sort to belt his bat into the ground; he very gently places it on the floor as he waits for Morkel. He's quite square on, turning his head so he is looking down the pitch with his head turned straight at the bowler. When an inside edge brings him a single, he shadow-bats some straight strokes. Good stuff, this. A real contest between bat and ball.

Mark Boucher
Former South Africa wicketkeeper on BBC Test Match Special

"This wicket will play well for the first two and a half days. After lunch tomorrow you will start to see variable bounce."

Cook is looking authoritative. Dark hair, square jaw. Trustworthy. Playing every ball on its merits, defending when Abbott is good, pushing for a couple when it's a touch too wide. It all looks in good order.

That's nice from Compton, who pounces on a Morkel short ball to pull for four. Is there a hint that Compton is warming to the task? There's never a great suggestion that he feels in. It's more like every time he walks out to bat he has to remember what he's doing all over again.

Mark Boucher
Former South Africa wicketkeeper on BBC Test Match Special

"I've a got a feeling that South Afica are starting to get into a bit of rhythm here. They know they'll have to take every chance to get to get into a position to win this match."

Image source, AP

Kyle Abbott is back into the attack, beating the tentative prod of Nick Compton with one that nips away. He's a moist man, Abbott - sweat covering his stubble and stringy hair. Compton scratches around, miscuing a single into the off side. It looks a tougher game for Compton than Cook at the moment.

Lovely, sunny evening in Centurion. It's warm enough to require a man with a backpack to go round the crowd spraying out water. It's a bit like he's wearing a Ghostbusters Proton Pack. Morkel, legs longer than a Grand National winner, gets good carry as Cook leaves alone.

Mark Boucher
Former South Africa wicketkeeper on BBC Test Match Special

"The problem with South Africa's bowling at the moment is they are just bowling one or two too many four balls. On a wicket like this Alastair Cook won't say no to a boundary."

Compton is away from his 15th delivery, pushing Rabada into the off side and sprinting like a man rushing for the last train home. Ooohhh, that's nice from Cook. Short and wide, cut for four. Meat and drink for Cook, who cuts like a Musketeer brandishing a rapier.

Mark Boucher
Former South Africa wicketkeeper on BBC Test Match Special

"Already we have seen some deliveries keeping a bit low and it only needs one or two to put some doubt in the batsmen's minds."

Morne Morkel is into the attack, round the wicket to Alastair Cook, who has a leg slip for company. Cook, remember, has been caught down the leg side on a couple of occasions in this series. Compton, still on nought, watches a couple of deliveries go past the off stump. One keeps very low. Not a great sign for England.

YU HIMM FUNG: It's the way Hales seems to get out which is a cause for concern constantly flailing outside off stump.

Three slips and a gully for the slippery Rabada, who is too wide and allows Cook to steer to third man for four. Cook, familiar three taps of the bat, crouch, top button of the shirt undone, defends when Rabada straightens up, then works the final ball fine for a single.

Richard Ryan: Serious thought to our two openers looking forward? Sooner the better.