Stuart Broad took the last two wickets and finished with 4-15 as England's bowlers finally hit form at the World Cup to secure an unlikely six-run win over previously unbeaten South Africa.
South Africa bowled England out for 171 at Chennai's Chidambaram Stadium but a varied and disciplined English attack took full advantage of a deteriorating pitch to dismiss the Proteas for 165 and secure victory with 14 balls remaining.
Having reached 124-3, South Africa lost four wickets for the addition of three runs across five overs.
With the tailenders exposed, paceman Broad took two wickets in four balls to wrap up the win. Spinners Graeme Swann and Michael Yardy tied up the batsmen and fast bowler James Anderson was able to take 2-16.
England was coming off a shocking loss to Ireland, which followed an unexpectedly tough win over Netherlands and a high-scoring tie against India.
"We've been involved in three very tight games of cricket so far in this World Cup," England captain Andrew Strauss said. "We're definitely doing our bit to advertise the 50-over format but we'd like games to be a little bit less close than they are."
An eighth victory in nine completed matches against South Africa should help England take one of the four quarterfinal berths on offer in Group B. With three games remaining, South Africa is almost certain to advance as well - despite the loss.
Strauss' decision to bat first looked to have backfired spectacularly when Robin Peterson dismissed both England openers in the first over. Peterson also removed Ian Bell with a full-length diving catch off his own bowling for a spell of three wickets for three runs in 16 balls - finishing with career-best figures of 3-22.
Fellow spinner Imran Tahir took 4-38 to take his tournament tally to 11 wickets, leaving England's hitherto wayward bowlers to defend what seemed a paltry total.
But a vastly improved fielding performance and some tight bowling from all quarters secured an immediate recovery from Wednesday's upset loss to Ireland.
"Just goes to show, if you believe you can win a game, you can - as Ireland proved the other day, as we proved today," England spinner Swann said in a post-match TV interview.
South Africa's collapse made Jonathon Trott and Ravi Bopara's 99-run stand for England's fourth wicket look even more impressive than it already did in an innings featuring only one other double-digit score.
Trott eked his way to 52 the partnership with Bopara, who justified his selection ahead of Paul Collingwood with a gritty 60 that earned the man-of-the-match award.
"I don't think it was one of our best wins ever because we batted poorly really," Strauss said. "To lose three wickets early on a surface like that was criminal. Thankfully Trotty and Rav got us back in the hunt, but you're not going to defend 170-odd very often so we needed things to go our way."
South Africa captain Graeme Smith was first out in reply, falling with the score on 63 to a contentious caught-behind decision that sparked the loss of the first three wickets for 19 runs.
Broad's pace forced Hashim Amla (42) to play on to his wicket and his accuracy drew Jacques Kallis into an outside edge to Matt Prior. Sportingly, Kallis paused only to ask the wicketkeeper if he had grasped the low catch cleanly before walking back to the pavilion.
AB de Villiers, who scored a century in each of his two previous innings, and Faf du Plessis crawled along to add 42 for the fourth wicket before Anderson beat De Villiers with a ball that faintly brushed the bails to send them gently dropping to the ground.
The contact was so faint that it took a second or two for the England players to celebrate. The jubilation was more immediate as two more wickets fell with the score still on 124.
Bell fielded the ball quickly at short leg and flipped it back to Prior, who whipped off the bails to run out the retreating Faf du Plessis for 17. JP Duminy successfully referred a caught behind decision before Anderson bowled him just two balls later.
Peterson was caught behind off Yardy to make it 127-7 but a 33-run stand between Morne van Wyk and Dale Steyn held England up for six sluggish overs before Bresnan bowled van Wyk for 13.
South Africa needed 12 from 22 balls with two wickets left, but Broad trapped Steyn lbw with the first ball of the 48th over and had Morne Morkel caught behind three balls later to finish it off.
But the pitch's unpredictability had been obvious early on.
Strauss holed out to De Villiers at deep midwicket without scoring and Kevin Pietersen was caught at slip by Kallis. Peterson, whose previous one-day best was 3-42, then took a return catch off Bell's forward prod to leave England reeling at 15-3.
Trott successfully referred an lbw appeal when he was on 20 and was spilled by Steyn on 51, but fell just three balls after the second reprieve, caught and bowled by Tahir.
Prior edged Morkel to Van Wyk for 10 and Bopara equaled his one-day best score, set against India in Kanpur in 2008, before his 98-ball innings ended lbw to Morkel. Bresnan went lbw to Steyn, Imran Tahir had Yardy caught by Peterson, Broad fell lbw to Tahir and Swann was caught off Tahir as England's last six wickets fell for 37 runs.
"There was a lot on offer for bowlers today: reverse swing and inconsistent bounce," Smith said. "There are a lot of batters' days in one-day cricket. I suppose this was a bowlers' day."
