Lamb, earning her third ODI cap and playing in just her fifth game for England across all formats, looked every inch a seasoned international star as she struck 102 off 97 balls to drive England's chase of 219 at Northampton.

Tammy Beaumont (1) fell early, bowled by a beauty from Marizanne Kapp (1-45), but the hosts were otherwise largely untroubled, with Nat Sciver (55) also firing a 31-ball fifty as England romped to victory with a massive 107 balls to spare.

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It means England lead the multi-format series 4-2 following off the back of the drawn Test match between the two sides. They next meet on Friday for the second ODI in Bristol, while three T20Is follow at the conclusion of the 50-over series.

Sciver also impressed with the ball, claiming 4-59 as South Africa were bowled out for 218 in 47.4 overs. But it was Katherine Brunt who was the pick of the bowlers - back in the team, having retired from Test cricket - as she claimed 3-18 from her nine overs.

Brunt took two of those wickets in her opening five overs, while Sophie Ecclestone (1-30) bowled captain Sune Luus (7) to have South Africa three down early on.

Laura Wolvaardt played cautiously for 43 but when she fell in the 30th over - lbw to Charlie Dean (1-54) - the tourists were in big trouble at 108-5, but Chloe Tryon cracked 88 off 73 balls to at least see South Africa up beyond 200 and to a reasonably competitive score.

She and Nadine de Klerk (38) shared in a Proteas record 97-run partnership for the sixth wicket against England, though when Tryon finally perished in the deep looking for a fourth six of her innings, South Africa quickly collapsed thereafter losing their last five wickets for 13 runs in 16 deliveries.

In reply, England could be forgiven for being a little rattled as Kapp burst one through Beaumont's defences in the third over, but Lamb, with fine support first from Sophia Dunkley (22) and then Sciver, calmly set about their target.

Lamb's fifty was reached in 51 deliveries, while her hundred - containing 15 fours - was brought up off just 91 balls.

De Klerk (2-44) dismissed Dunkley lbw and ended Sciver's blistering knock, caught at deep midwicket, while Lamb herself fell 17 runs short of victory and skipper Heather Knight (20) even closer, but an opening win of the series was never in doubt.

Watch the second one-day international between England and South Africa, live on Sky Sports Cricket on Friday. Coverage begins at 1.30pm, with the first ball at 2pm.