Postpublished at 16:00
So, according to Geoffrey, England have it all but wrapped up.
Is he right? (Is he ever wrong?) Join us tomorrow to find out.
Finn takes three wickets and Stokes one
Bairstow missed tough De Villiers stumping
South Africa need 416 to win
Bairstow 79 & Root 73 in England's 326
Stephan Shemilt
So, according to Geoffrey, England have it all but wrapped up.
Is he right? (Is he ever wrong?) Join us tomorrow to find out.
Geoffrey Boycott
Ex-England batsman on BBC Test Match Special
"There's a 1% chance of South Africa winning and 2% of saving it. I would be amazingly surprised if England don't win. Amla, the South Africa captain, is under immense pressure."
England fast bowler Steven Finn, speaking to Sky Sports: "We built pressure nicely after tea. We knew they were going to come out and go for it. They played really well and maybe we chased it slightly before tea.
"It's tricky to know when to attack and when not to attack and as a team we can go through the gears. Ideally, we would have seen the back of De Villiers, but we have created pressure there and he'll be a tough wicket for us tomorrow.
"When we went out there we had a target in mind of what we wanted to set and hopefully that will be vindicated tomorrow. We'll come back tomorrow and try and dry up those runs and hopefully that will bring us those wickets."
Geoffrey Boycott
Ex-England batsman on BBC Test Match Special
"De Villiers is a class apart, he just has so much time to play his shots, he looks comfortable. Lesser players play and miss an odd time, but he doesn't look in any trouble. He's the big fish they need to get tomorrow."
Former England captain Michael Vaughan: "We have to make Test cricket cheaper to watch and that is especially true in England where the prices can be outrageous.
"We almost have to look at Test cricket like the county championship. The one-dayers and Twenty20 can pay for Tests. If we have to give tickets away for Test matches then let’s do it. Seeing rows and rows of empty seats is a poor advert. The casual TV viewer will turn over thinking why should I bother?
"The product itself is not what it used to be. The standard of Test cricket has declined. There are three decent teams at the top. The rest are fairly average and in most cases declining further."
Meanwhile, there's some interesting stuff from Michael Vaughan in his column for the Telegraph..., external
Geoffrey Boycott
Ex-England batsman on BBC Test Match Special
"The pitch is slower and lower and didn't do anything for the seamers. The openers got their heads down and looked comfortable but Finn and Moeen have the gift of getting wickets. He gets four wickets a Test match does Finn - that's huge. He'd play in my team every time."
England have won only one of their last 15 Test matches overseas. That run dates back to 2012. Even though they won the Ashes in the summer, they are still without a win in four matches. They are six good bits of cricket from halting that run.
Geoffrey Boycott
Ex-England batsman on BBC Test Match Special
"England had such a wonderful day. Root and the tail got us off nicely and then it was the Bairstow show. The timing of his shots were superb. He played the first and second innings perfectly and he was the only batsman that played with any fluency. It was a shame that he got out, but that is his nature."
#bbccricket
Rob Parrett: Fair play to Cook. That was a sharp catch - you don't often see slips take catches on the inside!
Jon Buckley: Thanks Mr Finn. Like England I was flagging at the end of a day in the office. Celebrations (other Xmas chocs available) all round.
Geoffrey Boycott
Ex-England batsman on BBC Test Match Special
"The stumping chance went quickly, you have to take them, but it was difficult, and it would have been a big wicket to get De Villiers. If you get him out I feel the others are nothing special. I joked to the South African commentators that we could have asked for the extra half an hour because of their tail being so weak."
Yep, when England needed something special, they got it from the extra pace of Steven Finn. The Middlesex man delivered three big wickets - Dean Elgar, Hashim Amla and Faf du Plessis. Remember, Finn has the best strike-rate of any bowler to take more than 100 Test wickets for England since 1914.
Geoffrey Boycott
Ex-England batsman on BBC Test Match Special
"It was a wonderful day's cricket especially for England who played almost perfectly except for the Bairstow missed stumping off the best player in the world, De Villiers."
Graeme Swann
Ex-England spinner on BBC Test Match Special
"It was a great last over by Steven Finn, a great pace, good areas and got the vital wicket. He looked really solid and England are receiving a great cheer from the fans as they walk off."
South Africa need 416 to win
South Africa second innings: 136-4 (47 overs)
Batsmen: De Villiers 37, Steyn 0
Fall of wickets: 53-1 (Van Zyl 33), 85-2 (Amla 12), 88-3 (Elgar 40), 136-4 (Du Plessis 9)
Bowling figures: Broad 11-4-25-0, Woakes 6-2-17-0, Finn 9-3-27-3, Stokes 7-1-26-1, Moeen 15-3-36-0
England second innings: 326 (Bairstow 79, Root 73, Piedt 5-159)
South Africa first innings: 214 (Elgar 118 not out, Broad 4-25, Moeen 4-69)
England first innings: 303 (Compton 85, Taylor 70, Steyn 4-70, Morkel 4-76)
SA 136-4
Steven Finn fizzes one past the edge, but Dale Steyn gets through. England will sleep well after another very good day. They will return tomorrow hunting the six wickets that will put them 1-0 up in this series.
#bbccricket
JoElle: BOOOOM!
Tattz: A delivery for which the term 'rip-snorter' was invented. Great bowling from Finn!
bROCKerz: "Fiiiinn, Finn will tear you apart again!"
Steyn will do all he can to ensure this is the last over of the day. A whole host of slips and a short leg. Steyn survives one ball. Finn is bowling gas.
Jonathan Agnew
BBC Test Match Special
"What a good ball, and a lovely catch by Cook. It's not De Villiers, it's Du Plessis, but it will do. That's a really good wicket to have, it's just given them a lift."
Finn has been the man to make things happen for England today. He's got 3-27, this time using all of his 6ft 7in to find the bounce to remove Du Plessis. Dale Steyn, bad shoulder and all, has shuffled out as nightwatchman.