England 219 for 5 (Lamb 102, Sciver 55) beat South Africa 218 (Tryon 88, Wolvaardt 43, Sciver 4-59, Brunt 3-18) by five wickets
Emma Lamb stood up to the challenge set down for her ahead of this multi-format series with a stunning century in just her fourth international appearance to lead England to a five-wicket victory over South Africa in their first ODI.
After an assured 38 and sharing a 65-run partnership with Tammy Beaumont in that match, Lamb held her place in a revamped top order for the first of three ODIs which also included Sophia Dunkley batting at No. 3 for the first time in 20 matches in the format.
Playing just her third ODI - she scored a duck during the Ashes and wasn't required to bat against Pakistan at the World Cup - Lamb took charge at Wantage Road following the loss of Beaumont, brilliantly bowled by Marizanne Kapp with the 17th ball of England's reply as they sought 219 to win.
With Heather Knight at the other end, Lamb brought up her century with a stunning open-faced drive, inviting an enthusiastic embrace from her captain.
Lamb's cut shot was particularly productive as she repeatedly carved away anything wide of off stump, including the first of three fours in one Nonkululeko Mlaba over to bring up her fifty at almost a run-a-ball.
By the time Lamb fell for 102 from 97 balls pulling Tumi Sekhukhune to Ayabonga Khaka at square leg, just 17 runs were needed. After Knight was trapped lbw by Khaka, it fell to Danni Wyatt, who has routinely switched between opener and finisher in recent times and came in at No.6 on this occasion, to hit the winning runs, lofting Sekhukhune over mid-on for four to put England ahead on points 4-2.
Earlier, Sciver had claimed four wickets after Katherine Brunt, her wife, roared back into international action with a miserly 3 for 18 to bowl South Africa out for 218 inside 48 overs.
Had it not been for Chloe Tryon's powerful hitting to reach 88 off 73 deliveries, the equation could have been much worse for the visitors.
Brunt, back after announcing her retirement from Tests ahead of the Taunton game, unleashed an opening spell of 5-1-5-2 which reduced South Africa to 34 for 2 inside the first nine overs.
Only Laura Wolvaardt appeared to offer any resistance as South Africa then lost captain Sune Luus and the in-form Kapp cheaply. But when Wolvaardt was apparently pinned lbw on 43 by Charlie Dean and walked straight off despite replays suggesting she had laid a feather of bat on ball, Tryon took her cue to push South Africa somewhere towards a respectable total.
Returning to the side after she missed the Test with a hip injury, Tryon smashed 10 fours and three sixes on the way to her score. She twice overturned lbw dismissals to Sophie Ecclestone, on 34 and 69, one going over leg stump and getting an inside edge onto the other.
Tryon brought up her fifty driving Dean crisply through extra cover for two and in the next over she creamed two sixes off Kate Cross onto the roof of the stand beyond deep midwicket and over wide long on. She eventually holed out to Cross at deep midwicket off Sciver, ending a 97-run partnership with Nadine de Klerk, who added 38.
Tryon's wicket sparked a collapse in which South Africa lost their last five wickets for 13 runs in the space of 16 balls. Sciver, who had bounced back from an initial three-over spell costing 21 runs to claim the important wicket of Kapp, had Trisha Chetty caught behind four balls after removing Tryon and then Brunt returned to the attack and bowled Khaka with her second ball back.
Brunt had removed Andrie Steyn - opening after Lizelle Lee's shock retirement from international cricket last week - lbw for just 14 with a full ball that nipped back and thudded into the pad in line with middle stump.
Lara Goodall, on 5, overturned her lbw dismissal to Brunt with replays showing the ball to have pitched outside leg by a stitch but, two balls later, Brunt put the question beyond doubt with one that lifted off the seam and found a thick outside edge which went straight to Knight at slip.
From there South Africa's innings moved sedately at best until Tryon arrived to shake things up.
There was late drama when Cross slid at deep midwicket to parry a ball struck by de Klerk to Dunkley, who gathered and threw to the bowler's end where Sciver removed the stumps with Sekhukhune well short of her ground. Cross stayed down for a long while clutching her knee but she didn't look seriously hurt once she got up. De Klerk fell two balls later, well caught at mid-off by Ecclestone off Sciver to end South Africa's innings.
Valkerie Baynes is a general editor at ESPNcricinfo