England claimed a thrilling six-run victory over South Africa in Chennai to get back on course for the World Cup knock-out stages.
England posted just 171 on a turning wicket and looked set to slump to another defeat after South Africa moved to 63 without loss.
Even at 124-3 the result did not look in doubt, but three wickets in four balls changed the complexion of the match.
An eighth-wicket stand of 33 between Dale Steyn and Morne van Wyk tilted an intriguing contest back into South Africa's favour again, before Tim Bresnan broke the partnership and Stuart Broad (4-15) took the last two wickets in four balls as the Proteas slumped to yet another agonising World Cup defeat.
After losing to Ireland on Wednesday, England needed to bounce back against the tournament favourites, but were quickly in trouble after Andrew Strauss won the toss and batted, losing both openers to Robin Peterson (3-22).
Strauss unaccountably picked out the only fielder in the deep on the leg side, launching Peterson towards the mid-wicket boundary where Francois du Plessis took a good catch on the move.
Pietersen clubbed his second ball through mid-on for two - only to push forward to the next and edge to Jacques Kallis low at slip.
Peterson quickly had his third wicket when Ian Bell was beaten in the flight and pushed a drive back at the bowler, who dived to his left to take a smart return catch.
The spinner was surprisingly replaced by Jacques Kallis at the Press Box end, allowing Jonathan Trott and Ravi Bopara a little breathing space.
Trott survived an umpire review to post an 87-ball 50, and Bopara would later follow suit at exactly the same tempo. But by then his partner was gone to Tahir's diving return catch.
Matt Prior could lend only temporary support, before guiding an edge behind off the pace of Morne Morkel.
Bopara, who had justified his recall by equalling his previous best score of 60, was pinned lbw on the back foot by a short ball from Morkel that stayed low.
Steyn then quickly made it 149-7 when Bresnan departed in similar fashion, and England's second slump saw their innings quickly wrapped up well inside the 50 overs.
Hashim Amla was significantly more comfortable than his captain Graeme Smith in a half-century opening stand which suggested South Africa would stroll to victory and maintain their perfect start.
Yet both went in quick succession. Smith, pushing forward at a Graeme Swann off-break, was adjudged by the TV review umpire to have nicked it with his glove.
Then the introduction of Broad, the fifth bowler used after Strauss had opted to start with spin, brought the wickets of Amla - chopping an attempted off-side steer onto his stumps - and Kallis, caught behind low down.
AB de Villiers and du Plessis appeared to steady South African nerves with a stand of 42, until both went on 124.
James Anderson returned to bowl De Villiers, and impressive reactions from Bell at short-leg were enough to run out Du Plessis - who had gone up the wicket to Swann.
Anderson then knocked back JP Duminy's off-stump without troubling the scorers, and Mike Yardy had Peterson edging behind, as South Africa hit the buffers.
But when Steyn struck Pietersen back over his head for a resounding four, it looked as if the momentum had changed again.
Anderson failed to hold a tough one-handed return chance from Steyn on 15 shortly afterwards, but Bresnan returned to tempt Van Wyk to chop on.
Still Steyn would not be moved until, with eight still needed in the 48th over, Broad was back to see him off lbw with a superb inswinger.
Tahir managed to get off strike but Broad was not to be denied and immediately had Morkel edging an attempted drive, launching scenes that had as much to do with relief as celebration.