By CricketCountry Staff
London: Aug 18, 2012
Petersen was 20 not out and Proteas captain Smith 13 not out, with the tourists now 27 runs in front.
However, England got both the openers out early in the final session of the day. Amla along with Jacques Kallis stitched an 81-run partnership for the third wicket.
South Africa, 1-0 up in the three-match series, only have to avoid defeat at Lord's to replace England as the world's top-ranked Test side.
Both teams had collapsed to 54 for four in their first innings but Petersen, who hit two fours off James Anderson before elegantly driving Stuart Broad to the cover boundary, and left-hander Smith held firm.
Earlier on Saturday, Jonathan Bairstow fell just short of a maiden Test hundred as England took a slender first innings lead of six runs, making 315 in reply to South Africa's 309.
But the recalled Bairstow had the consolation of posting a Test-best 95 after coming in when England had slumped to 54 for four.
There was extra pressure on the 22-year-old Bairstow's shoulders as he'd been brought in to replace Kevin Pietersen, dropped despite scoring 149 in the drawn second Test at Headingley.
Brief Scores: South Africa 309 & 145 for 3 (Hashim Amla 57*, Jacques Kallis 31; Steven Finn 1 for 28) lead England 315 (Jonny Bairstow 95, Ian Bell 58; Morne Morkel 4 for 80, Dale Steyn 4 for 94) by 139 runs