A battling half-century from JP Duminy and a test best 46 not out from tailender Vernon Philander led South Africa's fightback as they closed on 262 for seven on the first day of the third and final Test on Thursday.
Play ended early due to bad light and a power cut. Three of the four floodlights were functioning when the players left the field with 14 balls left. Dale Steyn was also unbeaten, on 21.
England must win the match at Lord's to square the series and retain their number one status in the world rankings. South Africa will leapfrog them with a draw or win.
England shaded the day because of the placid nature of the Lord's pitch that traditionally encourages first innings totals in excess of 400, but nonetheless, the tourists have posted a competitive score.
Fast bowler Steven Finn wrecked South Africa's top order with three wickets in seven balls, before they rallied.
Philander came to the crease at number eight with his team 163 for six, while Duminy scored 61 before he perished to the third delivery with the new ball in the last hour.
The pair shared a seventh-wicket partnership of 72 until Duminy went to the fourth catch of the day for wicketkeeper Matt Prior, off James Anderson.
Finn ended with three for 68 and Anderson had three for 58.
Philander began fortuitously by edging two boundaries through third man off the edge but settled into his innings in which he had faced just 64 balls by stumps.
South Africa had elected to bat but crashed to 54 for four, when captain Graeme Smith (14), fellow-opener Alviro Petersen (22), Hashim Amla (13) and Jacques Kallis (3) all departed before lunch.
Smith jabbed at a wide ball from Anderson, who had come around the wicket for the first time, and was caught by Prior - but only after England lodged a successful review of umpire Kumar Dharmasena's decision.
Finn then claimed Petersen and Amla within four balls. Amla was bowled after Finn cut one down the famous Lord's slope and through the gate.
The biggest talking point of the morning was the loss of Kallis who was caught down the leg side by Prior via a deflection off his glove after Dharmasena initially rejected the appeal.
England called for a review and replays seemed to show the ball had clipped Kallis's bottom glove but only when his hand had left the bat handle. Third umpire Rod Tucker over-ruled the original decision and Kallis walked off, shaking his head in annoyance.
AB de Villiers (27) was reprieved after an England review for an lbw decision against Anderson that looked out, but he had not added another run before edging Anderson to Alastair Cook at third slip.
Rudolph stuck around with Duminy in a stand of 58 but he gifted his wicket, trying to clip an innocuous delivery from Swann to the on-side for a single but managed only an inside edge on to his pad and then the stumps.