The hosts have won all three ODIs after drawing the Test, meaning Heather Knight's side will seal the series outright with a victory at Chelmsford on Thursday evening
Leicester: England 371-7, South Africa 262 - England win by 109 runs
Tammy Beaumont led the way with a century as England thrashed South Africa in Leicester to ensure they cannot lose the multiformat series between the sides.
The hosts have won all three ODIs after drawing the Test, meaning Heather Knight's side will seal the series outright with a victory at Chelmsford on Thursday evening.
On this evidence, that seems a likely outcome; South Africa were desperately poor in the field and were second-best for almost the entirety of a boiling afternoon at Grace Road, where Sune Luus won the toss and inexplicably elected to field despite the crippling heat.
The result was a ragged performance, which began with a front-foot no-ball and scarcely improved. Emma Lamb passed fifty for a third consecutive ODI, with Sophia Dunkley also reaching another half century in her new role at No.3.
Both batted around Beaumont, playing her first game since being dropped from England's T20 squad for next week and the subsequent Commonwealth Games campaign. She hit 19 fours and a six in her 119, facing just 107 balls in the process. She fell in the 34th over, seemingly struggling with cramp, but having done more than enough already to put England in an unassailable position.
The only surprise was that the home team couldn't quite overhaul their ODI record total, set six years ago against Pakistan. The decision to rest Nat Sciver took some of the firepower from England's middle order, but even so Knight raced to 63 and Danni Wyatt smoked 33 in a 14-ball cameo.

Marizanne Kapp launched a defiant counterattack for South Africa (Dan Mullan/Getty Images)
Shabnim Ismail bowled just seven overs for South Africa, while Marizanne Kapp used just half her allocation. Instead, Nadine de Klerk's eight overs cost 87 runs. The tourists were sloppy in the field, with catches going down in consecutive deliveries at one stage, with a straightforward runout missed two balls later. When Kapp held onto a fine catch to dismiss Wyatt, there was hardly an acknowledgement from her teammates.
In reply, chasing a would-be South African record total for victory, Laura Wolvaardt gave England plenty to think about. She made a watchable half century, hitting 11 fours in her 56, only to miss a sweep shot off Charlie Dean to be trapped in front. By then, Dean – the leading wicket-taker in the series – had already bowled Andrie Steyn with the first ball of her spell.
Luus fell cheaply, missing a pull shot off Lamb to give the youngster her maiden ODI wicket, while Alice Davidson-Richards also claimed her maiden 50-over scalp for England, with Lara Goodall miscuing to mid-on. They were held up thereafter by the partnership of the innings between Kapp and Chloe Tryon, who added 110 in 15.3 overs, both reaching fifty and adding much-needed fight to a meek overall display.
Kapp eventually fell to Lamb, while Tryon was caught at long on to give Dean another wicket. By the time the final wicket had fallen, with Alice Davidson-Richards bowling Ayabonga Khaka for her third wicket of the evening, the game was long since finished as a contest.