Home side were bowled out on the second day of the first Test at SuperSport Park
England needed just 11 balls to take South Africa's final wicket on the second day of the first Test at SuperSport Park on Friday.
South Africa were bowled out for 284, adding seven runs to their overnight total of 277 for nine.
Vernon Philander scored all the runs before he was caught behind off Stuart Broad for 35.
Both Broad and Sam Curran finished with figures of four for 58.
It could have been a lot better for England — and worse for South Africa. The hosts were in deep trouble at 111 for five before De Kock counter-attacked to make a half-century off 45 balls.
De Kock played some risky strokes early in his innings but was more circumspect after his initial flurry of strokes.
Having been 64 not out off 69 balls at tea, De Kock needed 59 balls to add 31 more runs before fellow left-hander Curran had him caught behind.
Curran was the best of the England bowlers, keeping a fuller length than his team-mates and slanting the ball across right-handed batsmen, with some balls swinging back in and others moving away.
Stuart Broad, recovered from illness, which prevented him from bowling in his team's two warm-up matches.
James Anderson, playing in his 150th Test — the first specialist bowler to reach the milestone — took a wicket with the first ball of the match when Dean Elgar nudged what looked no more than a leg side loosener to wicketkeeper Jos Buttler.
Elgar's fellow opener Aiden Markram also fell to a loose shot, clipping Curran to midwicket.
Zubayr Hamza, batting at number three in his third Test, played a promising innings of 39, which proved to be South Africa's second-highest score.
New cap Dwaine Pretorius made 33 and helped De Kock add 87 for the sixth wicket.
Ben Stokes was off the field for two extended periods after lunch and again after tea, suffering from dehydration. Stokes was in the England team despite his father, Ged, remaining in a Johannesburg hospital with a serious illness.
According to a team spokesman, there was no change to Ged Stokes' condition, which was described as "stable" on Wednesday.