Before all that drama, here's where England did the damage with that 110-run partnership between Bairstow and Roy...

Before Bairstow fell just short of a half-century.

Buttler got outside the line for that lbw shout - which is just as well, because it was going on to hit the stumps. Dane Paterson spears in another fin yorker before Liam Livingtone nervously clips away a single.

Jos Buttler takes a step down the track to Dane Paterson and flicks the ball off his pads for four. That was a lovely little touch. Chris Morris then draws the sarcastic jeers of the crowd as he misfields a simple stop at point, and England nab a crafty single. It's all happening as Paterson has a huge lbw appeal against Buttler turned down. That was a corker of a delivery - full, straight and striking Buttler on the toe.

Charles Dagnall
BBC Test Match Special

He's nicked it! That's why Chris Morris is chuntering. He'll feel very aggrieved.

There's a huge appeal from Chris Morris, he thinks he's got Liam Livingstone caught at slip - but the umpire says no! Livingstone came down the pitch, had a big swipe and the ball went flying to slip. It's hit his shoulder but Ultra Edge shows that there was a bit of bat on that. Chris Morris is an angry man right now.

There's a bit of spice in the field now as South Africa look to put the squeeze on. Local lad Jos Buttler is cheered to the crease by the crowd but he's got a fired up Chris Morris to deal with.

The ball has struck Roy on the heel of the foot - he had a big turning circle as he crossed the pitch to run the ball back in but for my money, that's not intentional from Roy. He wasn't looking at the ball... has he obstructed?

Charles Dagnall
BBC Test Match Special

I can't ever recall seeing an obstruction review before.

So nearly a run out! Jason Roy at the non-strikers wants a quick single, but he's sent back by Liam Livingstone. The ball comes in and misses but South Africa have appealed. They reckon Roy obstructed the path of the ball - and we're going upstairs...

Ruth Brooksbank‏: Great to see Jason Roy play the way we knew he could. England were right to stick with him.

Tabraiz Shamsi will continue and Liam Livingstone sweeps him over his shoulder, head tucked out of the way, for another couple of runs. The Lancashire batsman then wallops a cut shot that goes flying towards the boundary, but a green-and-yellow shirt is in place to cut it off.

Natalie Germanos
BBC Test Match Special commentator

Chris Morris is a wonderful guy and very down to earth but he can be intense and fiery on the field. He loves playing for South Africa and has a tattoo of his Test cap.

Liam Livingstone is at the crease on debut and gets an earful from Chris Morris as he knocks his first ball off his hip rather awkwardly. He gets off the mark with a nicely-clipped two, before Morris continues the verbals with Livingstone and Jason Roy.

Ebony Rainford-Brent
Ex-England batter on BBC Test Match Special

That's a big wicket and AB de Villiers is celebrating but you get the sense England have got this game in the bag.

Here's the cracking six that brought up Jason Roy's half-century.

That last boundary from Jason Roy brought up the 100 partnership for this duo. They've barely looked troubled. Tabraiz Shamsi is back and Jonny Bairstow sweeps him aerially for another four. It's Morne, who isn't having a happy day, who ends up diving aimlessly at the ball in an attempt to cut it off.

Vic Marks
Ex-England spinner on BBC Test Match Special

Morkel is looking a bit bemused. He can't find a length that works, partly down to the brilliance of Roy.

Morne's ticking. An 87mph bouncer comes Jason Roy's way, before Morne has a quick natter with the umpire about something. That'll not improve his mood - a genuine edge as Roy cuts outside off stump and the ball whizzes through the vacant third man slot and into the boundary. And another whacking pull shot from Roy to pick up yet another boundary rounds off a chastening over for Morne.