England 311 for 8 (Stokes 89, Morgan 57, Roy 54, Root 51, Ngidi 3-66) beat South Africa 207 (De Kock 68, Van der Dussen 50, Archer 3-27) bt 104 runs
London: Jofra Archer and Ben Stokes lit up The Oval to ensure England defeated South Africa and got their World Cup campaign off to a winning start.
Regularly bowling in excess of 90mph, Archer - playing only his fourth one-day international - 3-27 and hit Hashim Amla on the helmet to force him to retire.
After Stokes took an amazing one-handed catch on the boundary to dismiss Andile Phelukwayo, South Africa were dismissed for 207 as they lost by 104 runs.
Stokes earlier made 89 and Jason Roy, Joe Root and Eoin Morgan hit half-centuries to take England to 311-8, a total that seemed no better than par.
Quinton de Kock's 68 seemed to have South Africa in the hunt at 129-2, but he pulled Liam Plunkett to long leg to become the first of three wickets to fall for 15 runs.
When Stokes took two wickets in two balls, the world number ones and favourites completed an ideal start to the tournament.
In a competition where the 10 teams play each other once to determine the semi-finalists, the hosts travel to Nottingham to meet Pakistan at Trent Bridge on Monday.
South Africa, who showed enough with the ball to suggest they will contend for the semis, are back at The Oval on Sunday to take on Bangladesh.
England have been building to this competition for the four years since their dismal first-round exit at the last World Cup, sweeping all before them mainly thanks to their power-packed batting line-up.
But for three-quarters of a day that began with the Duke of Sussex opening the tournament, they were in danger of being upset by a well-drilled South Africa.
Indeed, on a slow pitch that produced intriguing rather than entertaining cricket, this was at times a low-key start to the tournament. Under grey skies even the crowd was subdued for long periods.
The exceptions to all of this were Archer and Stokes. For Archer, pace, aggression and hostility made it seem like a wicket was likely every time he had the ball in his hand.
However, the moment of the day belonged to Stokes, who took the most incredible catch, one that is unlikely to be bettered throughout the whole tournament.
As Phehlukwayo swept Adil Rashid towards the mid-wicket boundary, the ball seemed to be too high for Stokes to reach.
He leapt, flinging himself backwards with his right arm outstretched. As he clung on in one hand, the crowd gasped and his team-mates mobbed him for disbelieving celebrations.