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Here's the report on today's action.
As for tomorrow, can the skipper go where no England batsman has gone before? Can he lead his team back into this match?
Join us tomorrow to find out. Goodbye.
Summary
Cook 67*, Root 31*
Rabada removes Hales & Compton
Compton lbw to one that kept low
SA: De Kock 129*; Stokes 4-86
England lead 2-0 in four-match series
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Pawan, if it is a daddy from Cook tomorrow, then he will become the first England batsman to 10,000 Test runs. History beckons.
get involved Get Involvedpublished at 16:27 Greenwich Mean Time 23 January 2016
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Pawan Kumar: Finally, Alastair Cook gets going. Hoping a daddy hundred from him tomorrow.
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England all-rounder Ben Stokes on Sky Sports: "It was hard work Every time we got a wicket, they got a partnership. It was hard graft, but looking back the chance let us down and we let them off the hook. If we'd taken them, it could have been a different ball game.
"We know the Kookaburra ball will only swing for 10 or 15 overs, but we've still been surprised at the lack of sideways movement.
"There was no slacking off. We don't want to lose this game, we want to win it."
Postpublished at 16:20 Greenwich Mean Time 23 January 2016
get involved A trio of Cook hundreds?published at 16:20 Greenwich Mean Time 23 January 2016
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Could this be the first Test in which three Cooks have scored hundreds? With Alastair Cook looking set on 67* following Stephen Cook and Quinton de Kock (translated from Afrikaans as a "male chef/cook") scoring their maiden tons, I think the odds are good!
Ben Edwards
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Geoffrey Boycott
Ex-England batsman on BBC Test Match Special"Cook is a quality player. Who would I like to open with in a world XI? Alastair Cook. He plays like an opening bat."
get involved Get Involvedpublished at 16:18 Greenwich Mean Time 23 January 2016
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Charles Duncan: All this talk of England becoming more balanced, yet who is saving us yet again?
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Michael Vaughan
Ex-England captain on BBC Test Match Special"England will look to bat the majority of tomorrow but they will probably still have a deficit at the close. They have got a lot of batting to do."
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Geoffrey Boycott
Ex-England batsman on BBC Test Match Special"I can't see them getting bowled out."
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Jonathan Agnew
BBC Test Match Special"If England don't bat all day tomorrow then they're in trouble."
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But fears were allayed by the old, dependable pair of Alastair Cook and Joe Root. Cook 67 not out, Root unbeaten on 31. A stand of 60, but much, much more needed tomorrow if England are going to avoid defeat.
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Geoffrey Boycott
Ex-England batsman on BBC Test Match Special"Compton is solid and safe. I would have opened with him in this series instead of Hales. He may not be the ideal opening batsman but I want platforms. We've plenty of people who can move it on down the order."
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When Nick Compton was pinned by a grubber, it looked like England might be in trouble. Not just because they were 78-2, but because the pitch was starting to play tricks.
get involved The opener's conundrumpublished at 16:11 Greenwich Mean Time 23 January 2016
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Andy Donley: Conjecture on Hales' replacement is pointless. Next Test isn't till May. Whoever scores heavily domestically should play.
'Hales hasn't got it'published at 16:10 Greenwich Mean Time 23 January 2016
Geoffrey Boycott
Ex-England batsman on BBC Test Match Special"Hales' was a shocking shot - caught at cover as an opening batsman. I'll repeat that: caught at cover as an opening batsman. It's not humorous.
"The lad has never had it in Test cricket - he doesn't have the attitude for it. He hasn't got it. He's got wonderful hand-eye concentration but he's a one-day cricketer.
"Test cricket is a really examination of your technique, your temperament, when to play your shots.
"He's got one more innings to come. Even if he makes runs in the second innings, that's not enough. I need more consistency from my opening batsman. If the lad comes up to me I'll tell him exactly what I'm saying now."
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Image source, Getty ImagesDe Kock's unbeaten 129 really took the game away from England, who will have been looking to get back into the contest with a solid start to their reply.
Alex Hales, though, was loose again. Caught at point, more trouble around off stump. One last chance to cement his place?
Postpublished at 16:06 Greenwich Mean Time 23 January 2016
Geoffrey Boycott
Ex-England batsman on BBC Test Match Special"De Kock played splendidly, effortlessly. He looks to be a shot-player. He took a real liking to Moeen Ali - he just walloped him. It was all about him. Piedt did his job at the other end and left it to De Kock."
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Image source, Getty ImagesI think it's fair to say that England started and ended the day well. Early wickets in the morning, good batting in the evening. In between, they were blitzed by Quinton de Kock.
Postpublished at 16:04 Greenwich Mean Time 23 January 2016
Michael Vaughan
Ex-England captain on BBC Test Match Special"There's going to be more low bounce over the next three days. You're under a lot of pressure when a team gets 475 on the board - you're only one bad session away from losing the match. If England get out of this Test with something, they'll have done brilliantly."