Semaphore and shooters
It's all about planning
There were a few raised eyebrows when Stuart Broad had a deep square-leg in place while bowling to Jacques Kallis. After all, this has been a surface where the quicks have caused most of their problems by pitching the ball up and getting uneven bounce. Was it a double-bluff from Broad and Andrew Strauss? No, it was a perfect piece of planning. Broad, after drying up the runs, banged in his first short ball of the day, and Kallis obligingly pulled it to Alastair Cook on the boundary who, despite a mini-wobble, held on.
Early in the day, there was a lot of arm-waving going on between the pitch and scorers. It wasn't clear what the issue was until Brian Jerling, the fourth umpire, made his way up to the box, accompanied by a man with two large bulbs. It emerged that there were no indicator lights to enable the scorers to confirm they had registered the umpires' signals, and so instead they had to resort to semaphore. However, the man with the bulbs quickly went to work, and soon everyone's life had been made that bit easier.
Within an inch
England haven't had any luck with the review system in this match, and are pretty fed up with the whole process. Their mood won't have been enhanced when, desperate for a breakthrough, Andrew Strauss gambled on using his final review when Graham Onions had a huge shout for lbw against AB de Villiers. The replay looked good; it pitched in line, hit in line, but would have crashed pretty comfortably into leg stump, but under the parameters set for the margin of error, there was enough doubt still lingering for de Villiers to survive.
As has been the case since the second day, the crowd were allowed onto the outfield during the lunch interval. Among the many games that sprang up, one young boy caught the attention. He ran in with a neat action, bowled with a hint of swing and then switched to sending down a few leggies. When his turn came with the bat he was quickly into position to play the pull shot. Expect him to be offered a Kolpak deal within days.
England finally get one
Given they had spent another sweltering day in the field, England may just have lost the plot if JP Duminy had survived his lbw appeal against James Anderson on review. The ball pitched in line and swung nicely back into Duminy's pads so Steve Davis was happy to give it out. Height was the concern, but it went in England's favour - but only just. Replays showed the ball was only clipping the bails but, because it had originally been given out, the on-field call remained.
Hashim Amla had just reached his hundred by flicking Broad through midwicket and was seeing it like a football. Still, he had no chance of playing the grubber from Anderson that scuttled along the deck and crashed into off stump. Anderson barely celebrated, partly because South Africa's lead was out of reach, but mostly because he knew the challenge that was about to confront England in their second innings.
Clouds on the horizon?
During the fourth day, the sky became something other than perfectly blue for the first time in the game. The ominous sign of thunderclouds began forming in the distance - as the forecast had predicted - and they started to turn the sunshine hazy. This match has been notable because it's the first time here that an England game hasn't impacted by the weather. But there is still a day to go, and the visitors would welcome some help from above.
Andrew McGlashan is assistant editor of Cricinfo