Innings break England 414 for 5 (Bethell 110, Root 100, Buttler 62*, Smith 62) vs South Africa

Jacob Bethell cracked the first hundred of his professional career, issuing a timely reminder of his immense talent to launch England past 400 in Southampton. At 21, Bethell became the second-youngest England player to score a men's ODI hundred, underpinning England's total in a 182-run partnership for the third wicket with fellow centurion Joe Root.

Bethell's twin failures in England's fifth-Test defeat to India at The Oval have filled countless column inches over the last month, highlighting the low volume of cricket that he has played this summer. He acknowledged on Sunday morning that he could have played more, but his 76-ball hundred underlined that he is a special talent who deserves his rapid promotion to this level.

Having sealed the series with a match to spare at Lord's on Thursday, South Africa looked short of intensity or motivation. They rested Lungi Ngidi, their most experienced seamer, and were uncharacteristically sloppy in the field: Matthew Breetzke made a hash of an incredibly simple chance off Jamie Smith, but Nandre Burger's drop of Bethell on 44 proved particularly costly.

Retaining his spot at No. 4, Bethell took the initiative early in his innings by attacking Keshav Maharaj, the top-ranked bowler in this format. He punished the short ball, launched three straight sixes, and reached three figures with a rasping cover drive, celebrating his first senior century in his 141st innings across first-class, List A and T20 cricket.

Bethell has now made at least 50 in four of his six ODI innings this year and has confirmed his status as a certain starter in their white-ball teams. If he can continue his form on a white-ball tour to New Zealand in late October, he could yet displace Ollie Pope as England's No. 3 for the first Ashes Test in Perth.

Root played in Bethell's slipstream, reaching an effortless hundred - his 19th - in 95 balls. It was vintage Root: he hit only six boundaries but scored 50 singles, 10 twos and two threes to run South Africa ragged. For the second ODI series in a row, they conceded 400-plus in a dead-rubber after going 2-0 up with a game to spare.

England made their best start of the series after being asked to bat first by Temba Bavuma, reaching 59 in the ninth over before Ben Duckett's international summer ended with a top-edged pull to midwicket. Smith looked in fine touch, racing to his second half-century of the series, before he swung Maharaj straight to long-on for 62 two balls after the drinks break.

South African heads dropped during Bethell and Root's vast stand, and even two quick wickets in the 41st over - Bethell stumped charging Maharaj, and Harry Brook run out for the second time in the series while attempting a casual second - could not slow the scoring rate, as Jos Buttler and Will Jacks ensured a strong finish.

Buttler belted 62 not out off 32, launching Maharaj back over his head, scooping Wiaan Mulder for six and turning a ramp off Burger into a late deflection for four. Jacks' straight six off Burger doubled as a forewarning for the government's emergency alarm test, which set off a flurry of phones in the stands; a loft over cover took England past 400 for the seventh time in ODIs.

South Africa's bowling effort was encapsulated by them conceding 27 extras, including 19 wides, while Burger's analysis - 0 for 95 off 10 - was the most expensive in their ODI history. Codi Yusuf, on ODI debut, only narrowly avoided the feat himself in conceding 80 from his 10 wicketless overs of medium pace. Bavuma also suffered a calf injury in the field, with South Africa saying he would only bat only if required.