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Ffion Wynne
BBC Sport journalist
First T20, East London
South Africa 142-5 (20 overs): De Klerk 29* (16); Dean 2-20
England 143-6 (19.2 overs): Sciver-Brunt 59 (54); Marx 3-19
England won by four wickets
Nat Sciver-Brunt's composed half-century led England to a four-wicket win over a depleted South African side in East London.
Chasing 143, Sciver-Brunt fell for 59 in the final over with the scores tied but Sophie Ecclestone scampered a leg bye to secure the victory with four balls to spare.
South Africa were in a strong position when England needed 57 from the final six overs on a slow pitch, but Sciver-Brunt and Amy Jones smashed 22 from Ayanda Hlubi's 15th over to change the course of the game.
Jones fell for a crucial 31 from 19 balls in the following over, but South Africa's attack struggled without three of its frontline bowlers in Marizanne Kapp, Ayabonga Khaka and Chloe Tryon, who were rested.
Nadine de Klerk stepped up with 2-20 while seamer Eliz-Mari Marx took 3-19, but the recent T20 World Cup finalists were left to rue their sluggish start with the bat.
In the absence of two of their experienced batters in Kapp and Tryon, the Proteas' remaining senior players were guilty of squandering good starts with captain Laura Wolvaardt making 22, Tazmin Brits 15 and Anneke Bosch 18, while Sune Luus fell for a duck.
Annerie Dercksen held the innings together with 26 from 29 balls before De Klerk's impressive cameo of 29 from 16 provided a much-needed late flurry of runs to post 142-5.
It looked a competitive total on a turning pitch but Sciver-Brunt's class proved the difference for England, who take a 1-0 lead in the three-match T20 series before three one-day internationals and a four-day Test follow.
England respond to World Cup disappointment
In England's first outing since their disastrous T20 World Cup group-stage exit in October, they played with a more reserved style than the ultra-aggression that head coach Jon Lewis has tried to encourage.
But wins are the most effective form of currency in silencing critics and they managed that comfortably - starting with a solid, if not spectacular, all-round bowling performance.
Their only specialist seamer Lauren Bell did struggle, conceding 46 from her four overs, and leg-spinner Sarah Glenn also had difficulty in finding rhythm but Ecclestone and Dean were back to their best after tricky individual World Cup campaigns.
Dean claimed the big breakthrough of South Africa skipper Wolvaardt, deceiving the opener with a well-executed quicker ball, and then had experienced all-rounder Luus caught at mid-off.
Ecclestone's sole wicket was of opener Brits, who was stumped, but she conceded just 18 from her four overs and her swagger of confidence had returned - a sight that will certainly please England fans.
At 64-4 and with most of their senior batters back in the dugout, South Africa seemed destined to collapse but the spirited Dercksen ran brilliantly between the wickets to accumulate vital runs in a stand of 36 with Nondumiso Shangase, before De Klerk gave the Proteas a decent total with four fours in her entertaining cameo.
There were still a few fumbles in the field, and Sciver-Brunt dropped a simple catch off Bosch on 13 - it ultimately only cost a further five runs, but those are the small errors that England will be hoping to put right throughout this multi-format series and before the Women's Ashes start in January.
Sciver-Brunt steadies England again
After England had suffered a slight wobble of their own, reaching 64-4 at the halfway mark, Sciver-Brunt provided yet another reminder of her priceless presence in the middle order.
Openers Maia Bouchier and Danni Wyatt-Hodge provided a fast start with 28-0 from three overs, before the latter was bowled by De Klerk for 11 and Bouchier missed a reverse-scoop off seamer Marx to be bowled for 20.
The returning Sophia Dunkley was caught behind for four and Heather Knight was bowled by one that kept low from Marx for just one, leaving England reliant on their calm but ruthless all-rounder once more.
With the pitch getting slower and lower throughout the innings, Sciver-Brunt kept her game plan simple with strong shots through the covers, careful but consistent rotation of strike and powerful pulls when the inexperienced bowlers missed their length.
Jones played the perfect accompanying hand with her dynamic innings, brutally punishing 20-year-old Hlubi who was visibly nervous, bowling four front-foot no-balls in her spell of 0-40.
They ensured that the job was all-but complete for Freya Kemp and Ecclestone to tick off the remaining runs, as England's strength in depth prevailed over their opponents.
Kapp and Khaka would have certainly made a difference for South Africa, with the pair missing all three T20s, but they will be boosted by the return of Tryon for Wednesday's second match in Benoni.