|First one-day international, Bloemfontein:|
|England 399-9 (50 overs): Buttler 105 (76 balls), Stokes 57 (38)|
|South Africa 250-5 (33.3 overs): De Kock 138 not out; Moeen 3-43|
|England won by 39 runs (D/L method)|
England made their second-highest one-day international total to beat South Africa by 39 runs on the Duckworth-Lewis method in Bloemfontein.
Jos Buttler's 73-ball century helped the tourists to 399-9, with Ben Stokes, Alex Hales and Joe Root passing 50.
Quinton de Kock's unbeaten 138 off 96 balls kept the Proteas in contention.
But the loss of wickets at key times halted the home side's momentum before rain ended the game with them on 250-5 to give England a 1-0 series lead.
The second ODI in the five-match series is in Port Elizabeth on Saturday.
England continue positive approach
The batting effort of captain Eoin Morgan's men represents a continuation of the dramatic improvement in England's limited-overs cricket since their woeful World Cup of 2015, when they were eliminated in the first round.
Since then, they have won a one-day series against World Cup runners-up New Zealand and Pakistan, as well as being narrowly beaten 3-2 by world champions Australia.
They have also won five consecutive Twenty20 internationals since the World Cup in an overall run of seven successive T20 wins.
On Wednesday England attacked throughout most of their innings, with Jason Roy taking early advantage of some tame home bowling on a benign pitch. He scored 48 off 30 balls before he was first man out, caught by Farhaan Behardien at cover off Morne Morkel.
Roy's opening partner Alex Hales then came to the fore, adding 62 runs with Joe Root to take England to 130 before he too was caught at cover, by AB de Villiers off the bowling of Marchant de Lange for 57.
Buttler then came to the wicket, where he would remain for 17 entertaining overs of clean hitting that propelled the tourists towards their huge total.
Buttler did not feature in the victorious Test series against South Africa, but he demonstrated why he is so valuable to the one-day side by hitting 11 fours and five sixes in an innings of 105 from 76 balls.
Remarkably, the 25-year-old Lancashire player's hundred was the slowest of his four centuries in ODIs, with his quickest being the 46-ball ton he scored against Pakistan in Dubai last year.
|England's highest ODI totals|
|408-9 (50 overs) v New Zealand, Edgbaston, June 2015|
|399-9 (50 overs) v South Africa, Bloemfontein, February 2016|
|391-4 (50 overs) v Bangladesh, Trent Bridge, June 2005|
|365-9 (46 overs) v New Zealand, The Oval, June 2015|
|363-7 (55 overs) v Pakistan, Trent Bridge, August 1992|
In a particularly destructive three-over spell near the middle of England's innings, he scored 34 runs off the bowling of JP Duminy and Behardien.
He lost both Root (52) and Morgan (23) as partners during his innings before he fell himself, caught at cover by De Villiers off Imran Tahir.
A rapid 57 from Stokes (off 38 balls) and minor contributions from Moeen Ali and Chris Jordan maintained some momentum, but the tourists eventually fell just short of their best-ever ODI total of 408, scored against New Zealand at Edgbaston last June.
De Kock's knock in vain for SA
The odds swung even further in England's favour when David Willey bowled Hashim Amla for just six in the third over of South Africa's reply.
But Amla's opening partner, De Kock, and replacement at the crease, Faf du Plessis, counter-attacked with the largest partnership of the game - 110 in just 83 balls - before the latter picked out Hales with a pull to the deep off Moeen to depart for 55.
The potential for rain meant the Duckworth-Lewis total was never far from South African minds, but the loss of wickets at key times meant they were never able to keep pace.
De Villiers has not been in good form during the recent Test series between the sides but has three centuries in his last six ODIs. He fell to a brilliant running one-handed catch from Stokes at wide long-on off the bowling of Ali, who also dismissed Rilee Rossouw after Reece Topley had caught and bowled Duminy.
The rain eventually came to deny the game a fittingly dramatic finale with 16.3 overs remaining, De Kock and new partner Behardien at the crease and the home side 150 runs short.
England captain Eoin Morgan: "It is not a satisfying way to win the game but to start the series with a win is a big bonus. We put in a monumental effort with the bat and played with the aggressive brand we have done in the recent past.
"We spoke at the start of the series that we wanted to start in the right manner and the way the openers went about their business really set the tone for the innings.
"Jos [Buttler] is the only player we have in the changing room who is capable of getting a 40 or 50-ball hundred. I have played with a lot of guys around the world and he is up there. The chance to promote him up the order and give him the chance to build an innings is important for his game and we benefit when it comes off."