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England took three wickets on the fourth morning of the final Test against South Africa, but Hashim Amla's half-century stretched his side's lead to 254.
James Anderson got England going early at Centurion, dismissing Stephen Cook and AB de Villiers in the space of three balls, and Ben Stokes prised out JP Duminy as the Proteas reached 121 for four at lunch.
But Amla held firm on 50 not out to nudge England's eventual fourth-innings chase ever upwards.
South Africa will be keen to extend that as far as possible given Kyle Abbott's hamstring injury may leave them with just two seamers.
At 42 for one overnight, nothing but early wickets would do if England were to find a foothold.
Anderson has had a series to forget, missing the opener through injury then struggling for rhythm and - according to De Villiers - pace.
But having removed Dean Elgar with a beauty on the previous evening, he summoned his best spell of the tour.
After two overs for one run he struck at the start of his third, Cook tempted forward and feathering a simple catch to Jonny Bairstow.
That brought De Villiers to the crease and Anderson needed just two balls to prove actions speak louder than words.
The crucial delivery clocked in at 86mph, not enough to beat De Villiers on speed alone, but it was also perfectly-pitched and tailing in prodigiously.
De Villiers reviewed the lbw decision but it merely confirmed his second duck of the match and third in a row since taking the captaincy.
Having made nought only four times in his previous 172 Test innings, De Villiers may be giving strong consideration to handing the reins on at the end of series.
England were buoyant but hit a brick wall in Amla and Duminy.
They put on 57 vital runs, extending the fourth innings chase bit by bit, in 20 solid overs.
Amla appeared well at ease, soaking up balls until seeing one he fancied and stroking it to the ropes.
Duminy also played his part, scoring 18 of his 29 runs off Moeen Ali including a crisp six over midwicket.
He failed to get on top of Ben Stokes in the same way, failing to negotiate the swing and edging a big drive to Bairstow.
Amla wore a second blow to the hand of the innings after reaching 50 and Temba Bavuma saw off 27 deliveries to reach the break.