England, set 221 for victory, made 224 for four with 20 balls to spare.

Ian Bell top-scored with 88, with Eoin Morgan was 36 not out and Craig Kieswetter, who finished the match with a six off fast bowler Dale Steyn, unbeaten on 21.

Earlier, South Africa's 220 for eight after losing the toss saw England off-spinner James Tredwell take three wickets for 35 runs in eight overs.

The series concludes in Nottingham on Wednesday.