Quite a lot to go through from that session, and one that Hardus Viljoen will want to remember. 

South Africa were dismissed for 313 - the lowest ever score when everyone reached double figures, fact-fans. Viljoen ended up not out on 20, having hit his first ball in Test cricket for four.

Alex Hales didn't last long for England, scoring a solitary run before flashing outside offstump and nicking to slip. 

Viljoen then took a wicket with his first delivery in Test cricket, strangling Alastair Cook down legside. 

Compton and Root are still there, but looked constantly troubled. South Africa are in the driving seat. 

Image source, Rex Features

Michael Vaughan
Ex-England captain on BBC Test Match Special

"I plea with administrators to have more wickets like this, because it's great for Test cricket."  

Jonathan Agnew
BBC Test Match Special

"Root and Compton will be pleased to be going off, because that was torrid stuff."

Viljoen looks as if he's bursting every blood vessel as he steams in, full of effort. He gets some decent bounce, too, as Root looks uncomfortable, twice beating the outside edge. 

Mind you, James Taylor looks even more uncomfortable as he watches on with his pads strapped up. 

Just two off the over as Root clips one off his pads, and the players come of for lunch, with the home side having a spring in their step. 

Thomas Knights: Alarming how many times Cook is getting strangled down the leg side.

Andy Donley: Interested to know who the batsman with most legside-caught-wicketkeeper dismissals in Test history is. Has to be Cook.

What is Compton playing at? He's faced 28 balls without playing a shot, then suddenly decides to flash at a good length away-swinger outside offstump, missing completely. 

Steady, old boy.

Image source, Getty Images

Andrew Samson
BBC Test Match Special statistician

"Hardus Viljoen is the 20th player to have taken a wicket with his first ball in Test cricket, and the third South African after Dane Piedt and Bert Vogler."

There have been worse first overs in Test cricket. 

Viljoen hasn't stopped smiling after that first delivery, and he asked good questions of Joe Root, including a play and a miss. 

Michael Vaughan
Ex-England captain on BBC Test Match Special

"You feel unfortunate when that happens, but he did dangle his bat down there. Joe Root - the new batsman - is quite vocal on the pitch and it looks like a few of the South Africans are reminding him of the match situation."

Jonathan Agnew
BBC Test Match Special

"What a start. All those people struggle to get a first wicket in Test cricket and you get a caught behind with one down the leg side. Cook will be livid."

Right then, here come Hardus Viljoen for his first delivery in Test cricket...

Rabada is making Compton look very uneasy. He beats the outside edge with a beautiful length delivery, and is getting some decent movement out there. 

Michael Vaughan
Ex-England captain on BBC Test Match Special

"Nick Compton is being true to himself: he wants to be attritional and wear the bowlers down. Alex Hales appears to be caught in two minds."

Two for Cook off his pads from Morkel's first slightly wayward over. 

There can't be many times in Cook's career that he's been in a partnership where he's been the more attacking one out there. 

Image source, AP

Michael Vaughan
Ex-England captain on BBC Test Match Special

"Alex Hales is England's version of David Warner. He's not of the same standard, but Warner goes out to hit the ball. Hales has to go out there and whack it. If he's timid, he'll get out."

A testing over from Rabada, who has Compton looking uncomfortable with a short delivery, followed by one that just beat the outside edge. 

You can't accuse Compton of not playing his natural game. He hasn't looked to score any runs yet - the only two he has scored was from a defensive shot, but he's going to have his work cut out here. 

Morne Morkel into the attack now. 

Michael Vaughan
Ex-England captain on BBC Test Match Special

"Hales is in two minds. His front foot doesn't go anywhere near the line of the ball so he just goes with his hands. The real challenge for him now is to remember why he was picked - to be something different, something aggressive. He needs to look to score and hit the ball."