A half-century from Joe Denly, as well as contrasting forties from Jonny Bairstow and Joe Root, proved to be just enough as England survived a late flurry of wickets to beat South Africa by two wickets.
Adil Rashid had earlier finished with figures of 3/51 to help England draw the series 1-1.
In pursuit of 257 to win, England got off to a blistering start courtesy of Bairstow's 23-ball 43. Together with Jason Roy he took 21 runs from Lungi Ngidi's second over, and continued the assault on Beuran Hendricks to take England past fifty without loss after just 5.2 overs.
It was in stark contrast to the South African innings which had built steadily as they finished the first 10 overs with 36/1 on the scoreboard, Reeza Hendricks the man to go for 11, bowled by a beauty from debutant Saqib Mahmood which just barely clipped the off bail.
Quinton de Kock and new batsman Temba Bavuma continued to build a platform, taking the score on to 89 in the 21st over before Bavuma was trapped in front by Adil Rashid. There was some confusion as Bavuma reviewed the decision unsuccessfully, with it at first seeming that South Africa would lose their review, but as Ultra Edge was unavailable the review was retained.
Rassie van der Dussen was grateful for it too, as he was intially given out first ball, before his review showed the ball to be sliding past leg stump. He didn't last much longer though, as Moeen Ali, playing his first ODI since England's defeat to Australia in the group stages of the ICC Men's Cricket World Cup 2019, pushed through a slightly quicker ball, beating van der Dussen's back foot push to clean bowl him for 5.
England too suffered a collapse, as Bairstow's wicket in the seventh over was followed soon after by the dismissals of Roy, for a run-a-ball 21, and Morgan, for 9, both falling to Beuran Hendricks, and leaving the visitors 86/3 after 11.1 overs.
But Root and Denly combined for a solid 76-run partnership to prevent panic descending on the English dressing room.
It was a role which had earlier been provided for South Africa by de Kock as he held the innings together along with JJ Smuts. With that in mind, he will be frustrated with the manner of his dismissal as he looked to hit against the spin of Rashid, and being clean bowled for his trouble, dismissed for an 81-ball 69.
Just a few overs later Smuts was run out thanks to a fine stop by Tom Banton which provoked some confused running and left the set batsman short of his ground as Bairstow whipped the bails off.
Banton had a role to play with the bat too, coming in after Root was caught superbly at leg-slip by Bavuma for 49. He and Denly continued to build steadily towards their target, aware that another wicket would see South Africa past the specialist batsmen and into the all-rounders. Denly began to open up as he hit back-to-back sixes, the first of them taking him to a fourth ODI fifty, and second of the series.
And now Curran is out too!— ICC (@ICC) February 9, 2020
16 still needed, three wickets in hand😬 https://t.co/pDygzmXjNk
But with 25 more required for victory, not just one but two wickets fell, as first Denly was caught on the rope off the bowling of Ngidi, before Beuran Hendricks produced a peach of a delivery to take Banton's edge.
Nine runs later, Tom Curran followed them, and with just five runs left to win Rashid feathered a catch behind. Moeen Ali struck a four to bring scores level, though it looked to be in the air as it passed just wide of short cover, before chipping a single into a vacant area of the outfield to complete the chase.
England would have found their task far easier if it hadn't been for David Miller's charge late in the first innings. His death overs blitz brought him 69 runs in 53 balls, including a six from the final ball of the innings. Rashid was named as Player of the Match for his figures of 3/51.