Third one-day international, The Oval: England 296-7 beat South Africa 170 by 126 runs and win series 3-0 (two matches still to play)
Flintoff produced another compelling performance with bat and ball
England produced another fine display under Kevin Pietersen's captaincy to beat South Africa by 126 runs at The Oval and seal the one-day series.
The result put England 3-0 up with only the matches at Lord's and Cardiff left.
Ian Bell (73) and Andrew Flintoff (78 not out) took England to 296-7, a total South Africa never threatened to reach.
Samit Patel destroyed the lower order and took 5-41 with his left-arm spin, his best figures in all listed cricket, after he had earlier made 31.
On the sort of fast-paced wicket which South Africa's players often crave when playing at home, the tourists - who began the series threatening Australia's position at the top of the one-day standings - were thoroughly outclassed.
After sneaking over the line in the opener at Headingley, England have stepped up their game, annihilating South Africa at Trent Bridge on Tuesday and now winning with almost as much ease in south London.
Stand-in captain Jacques Kallis won the toss for South Africa, but the overcast conditions provided little swing.
Criticised so often in the past for failing to take advantage of the early fielding restrictions, England put the memory of some ultra-sluggish starts in previous matches firmly in the past.
They were initially helped, however, by an extraordinary over bowled by Makhaya Ntini, the fourth of the match, from which 17 runs were garnered.
Ntini bowled two no-balls and one wide, and Matt Prior took advantage of one of the free hits with a big six over mid-on.
The most attractive shots played by England came in the next few overs, including a fine shot from Prior, who stepped down the track to nonchalantly guide a high-velocity missile from Morne Morkel behind point for four.
Ntini continued to be one of the most profligate bowlers on show, and he was lofted by Bell for six shortly after being driven through cover for four by the same batsman.
He raced to his half-century off just 36 balls, a week after taking 69 balls over his 35 at Trent Bridge, albeit on a wicket that gave batsmen full reward for their shots.
When Bell and Prior brought up their 100 partnership from the first ball of the 16th over, England were cruising, but they got an unwelcome jolt from the gentler pace offered by Kallis's swing bowling and Johan Botha's off-spinners.
Prior and Bell gave England a stunning start with a rapid stand of 101
Only 54 runs were scored from 80 balls as first Prior (33 off 37) top-edged into the covers, then Bell was lbw trying to push Botha for a single after his scoring rate had dipped to below a run a ball.
Kallis, with his first delivery, bowled Owais Shah for 23 just as the Middlesex man looked set for something big and followed up by dismissing Pietersen with a marginal lbw verdict in his following over.
South Africa were back in business and it needed two experienced campaigners, Flintoff and Paul Collingwood, to begin the healing process.
Attacking shots were shelved until the 34th over, when both came down the track to hit Kallis for fours, but former skipper Collingwood (14), back in the side after serving a ban, became Botha's second victim when he was caught by wicketkeeper Mark Boucher off bat and pad.
Flintoff was going well but needed strong support, particularly after being clattered flush on the helmet by a Morkel bouncer on 39.
And he got it from newcomer Patel, playing his first innings in ODIs, who scored quickly in a stand of 74 for the sixth wicket off just 67 balls.
Flintoff had to take several glugs of water and recover his thoughts after being hit on the head. The impact of the blow was such that he spent the first few overs of South Africa's off the chase off the field.
But before he could take his breather, he had work to do, and he struck nine fours, favouring the off-side with some beautifully-timed shots, and one tremendous six off Dale Steyn's slower ball.
Harmison's pace was too much for South Africa to deal with
With Luke Wright whacking a couple of fours at the death, England almost reached the 300-mark they had looked certain to cruise past after their first 15 overs.
But given that South Africa had been bowled out for 83 in Nottingham, England were firm favourites at the halfway point - a position only strengthened by the elbow injury to the tourists' regular captain Graeme Smith.
With the free-scoring Smith missing out, Hashim Amla took the vacant position at the top of the order.
James Anderson bowled seven immaculate overs which cost only 17 and included the wicket of Herschelle Gibbs, who stabbed a back-of-a-length delivery straight to short cover.
Amla battled away bravely and had reached 46 when nicking Steve Harmison behind. By contrast, Kallis produced a painful 25-ball innings in which he made just nine before skying Flintoff to mid-on, Patel running back to take a sharp catch.
South Africa's last vestige of hope evaporated when AB de Villiers was gormlessly run out as he took on Harmison's unerring throw.
Patel, bowling in the rather luxurious position of South Africa needing nearly eight runs an over, soon removed Boucher, and then caught Albie Morkel off his own bowling immediately after being swatted for two sixes by the same batsman.
Flintoff helped himself to another wicket as Pietersen strove to finish off the game.
And there were three more scalps for Patel - regarded very much as a batsman who bowls rather than the reverse - as South Africa folded in the 43rd over.