Their lead is only 2-1 with three matches to go in the next seven days but victory by 108 runs in the fourth encounter represented a considerable shift in balance. Since losing the first game, the home side have had the edge and yesterday they might have pushed England over it.
For the first time, the tourists looked like a side with one foot on the plane home. Not for the first time, the chief contributor to their cause was Kevin Pietersen, who provided the only reason for supposing that they might get close to their formidable target of 292.
That they were all out for 183 with nearly eight overs of their allotment unused was nothing to do with Pietersen, whose 75 was his third score above 50 in seven innings - though it reduced his average to 114. His booming batsmanship, full of bottom-handed thrust, is sufficient to draw him plenty of attention, although just to make sure, Pietersen is sporting a new hair-do which involves a broad blond streak down the centre and makes him look like Rocky Racoon.
The concern is that an England squad with clear potential will squander it over the next week in the face of an opposition who think they can at last see the wood for the trees. Michael Vaughan, the England captain, conceded that they will have to lift their game at East London on Wednesday, and he apportioned blame liberally and equally between bowlers and batsmen. South Africa, invited to bat by Vaughan, were allowed to score 40 or 50 too many, although they played to perfection the old trick of keeping wickets in hand to allow for the end-of-innings slog.
They scored 98 runs in the final 10 overs, 59 in the last five. Numbers three, four and five in the order all scored half-centuries and the middle one of those, Herschelle Gibbs, went on to a century, his 14th in one- day internationals.
When Gibbs was asked to move from his customary position as an opener at the start of this series, it looked like a panic move. The folly of this seemed to be compounded by his extreme reluctance, fuelled by the fact that he had scored 101 in his most recent limited-overs innings at the top of the order.
It now begins to seem like an inspired strategy which only men with profound technical and psychological knowledge could have suggested. Not attributes normally ascribed to South Africa's selectors but since Gibbs has had successive scores at No 4 of 78, 50 and 100, it is a theory that might not ship too much water.
Gibbs and Jacques Kallis put on 175 for the third wicket before Kallis was run out. Had he been dismissed in similar fashion 130 runs earlier, as he might have been when substitute Vikram Solanki's throw hit him, England would have been in the game. But his was the perfect setting for Justin Kemp to play another plundering innings.
The most expensive of England's bowlers was Stephen Harmison, who went for 65 runs in his 10 overs largely because he sprayed the ball this way and that in his early spell, putting Table Mountain, which overlooks the ground, in danger of permanent defacement.
Harmison received utterly unfair criticism yesterday for comments in the press about his homesickness. These were misconstrued by people who were not present and took light-hearted but candid asides out of context. Harmison may wish to go home - so do England - but the reason he bowled badly yesterday was down to poor form. He was used in five different spells and came back well.
The most unfortunate bowler was perhaps Kabir Ali, who conceded only 11 runs in his first six overs by adherence to the old bowling verities and was then despatched to all parts by Kemp. It was a learning experience.
If it was only a suspicion that England were out of it at the halfway stage, it did not take long afterwards to confirm it. The loss of the top three in 12 balls with the score in the early thirties made a difficult target more distant.
Pietersen fashioned what has become his usual variety of exciting shots and while he was there you never knew. He is making much of being back in his homeland, though he should never trust their barbers again unless he is thinking of forming a punk band. In the over he perished he struck, four, six, and another six before holing out high to midwicket. Six of his colleagues reached double figures, none made more than 20.
It was possible to question Vaughan's wisdom in fielding first, it was imperative to question the quality of the cricket that came after it. South Africa have made themselves outstanding favourites.
l Glenn McGrath picked up 5 for 27 as Australia beat Pakistan by 31 runs at the Sydney Cricket Ground to go an unassailable 2-0 up in the best- of-three VB Series finals. Damien Martyn top-scored for Australia as they reached 239-9 in their 50 overs, with Ricky Ponting making 41 and Adam Gilchrist chipping in with 40. The tourists were then dismissed for 208, with 26 balls remaining, despite 51 from Yousuf Youhana and a typically hard-hitting innings of 31 off just 21 balls from Shahid Afridi.
CAPE TOWN SCOREBOARD
England won toss
*G C Smith lbw b Kabir Ali 16 45 min, 27 balls, 1 four
A B de Villiers lbw b Gough 9 22 min, 14 balls, 1 six
J H Kallis run out (Collingwood) 71
140 min, 97 balls, 6 fours
H H Gibbs c Bell b Harmison 100
140 min, 115 balls, 8 fours, 3 sixes
J M Kemp run out (Giles-Jones) 57
53 min, 36 balls, 4 fours, 4 sixes
A G Prince not out 14
30 min, 11 balls, 1 six
Extras (b0, lb6, w18, nb0) 24
Total (for 5, 217 min, 50 overs) 291
Fall: 1-18 (De Villiers), 2-50 (Smith), 3-193 (Kallis), 4-227 (Gibbs), 5-291 (Kemp).
Did not bat: M V Boucher, S M Pollock, N Boje, M Ntini, A Nel.
Bowling: Gough 10-1-53-1 (w3) (6-1-21-1, 2-0-14-0, 2-0-18-0); Harmison 10-0-65-1 (w5) (3-0-24-0, 1-0-8-0, 3-0-16-0, 2-0-14-1, 1-0-3-0); Kabir Ali 10-1-58-1 (6-1-11-1, 2-0-11-0 1-0-16-0 1-0-20-0); Collingwood 5-0- 24-0 (w8); Trescothick 1-0-12-0 (w1) (one spell each), Giles 10-0-52-0 (w1) (8-0-33-0 2-0-19-0), Vaughan 4-0-21-0 (one spell).
Progress: 50: 43 min, 53 balls. 15 overs score: 62-2. 100: 103 min, 136 balls. 150: 135 min, 195 balls. 200: 173 min, 247 balls. 250: 198 min, 278 balls.
Kallis: 50: 108 min, 71 balls, 5 fours. Gibbs: 50: 84 mins, 73 balls, 6 fours. 100: 137 min, 114 balls, 8 fours, 3 sixes. Kemp: 50: 51 min, 34 balls, 3 fours, 4 sixes.
M E Trescothick b Ntini 13
33 min, 16 balls, 2 fours
G O Jones c Boucher b Ntini 19
23 min, 20 balls, 2 fours
*M P Vaughan c Kallis b Pollock 0
5 min, 6 balls
A J Strauss c Prince b Nel 17
48 min, 25 balls, 2 fours
K P Pietersen c de Villiers b Boje 75
111 min, 85 balls, 6 fours, 3 sixes
I R Bell c Boucher b Kallis 2
11 min, 8 balls
P D Collingwood c Boucher b Pollock 11
39 min, 23 balls
A F Giles c Pollock b Ntini 20
43 min, 31 balls, 1 four, 1 six
Kabir Ali run out (Gibbs) 1
11 min, 5 balls
D Gough not out 9
26 min, 21 balls
S J Harmison c Nel b Boje 4
9 min, 8 balls
Extras (b3, lb3, w6, nb0) 12
Total (184 min, 41.2 overs) 183
Fall: 1-32 (Jones), 2-33 (Vaughan), 3-35 (Trescothick), 4-73 (Strauss), 5-92 (Bell), 6-127 (Collingwood), 7-148 (Pietersen), 8-163 (Kabir Ali), 9-175 (Giles), 10-183 (Harmison).
Bowling: Pollock 10-0-35-2 (w1) (6-0-29-1, 4-0-6-1); Ntini 9-1-29-3 (w1) (6-1-19-2, 3-0-10-1); Nel 6-0-27-1, Kallis 6-0-36-1 (w3), Kemp 2-0-9-0, Boje 8.2-0-41-2 (w1) (one spell each).
Progress: 50: 55 min, 74 balls. 15 overs score: 67-3. 100: 104 min, 134 balls. 150: 149 min, 194 balls.
Pietersen: 50: 77 min, 60 balls, 5 fours, 1 six.
Umpires: I L Howell (SA) and S J A Taufel (Aus).
South Africa lead best-of-seven series 2-1.
TV replay umpire: B G Jerling (SA).
Match referee: R S Madugalle (S Lanka).
Man of the match: H H Gibbs.