|Graeme Smith survived an appeal on the fourth over of the day but was eventually bowled by Sidebottom after hitting his 20th Test century [AFP]
Graeme Smith hit a confident century as South Africa took control before heavy rain stopped play on the second day of the fourth and final Test against England at the Wanderers Stadium in Johannesburg
Smith was out for 105 shortly before a thunderstorm flooded the ground an hour before the scheduled tea break, with only 3.5 overs then being played after the interval.
South Africa were 215 for two at the final stoppage, a lead of 35 runs after England were bowled out for 180 on the first day.
Smith and Hashim Amla (73 not out) put on 165 for the second wicket.
The batsmen had to negotiate some hostile bowling at the start of an extended morning's play, with the ball swinging and moving off the pitch, but gradually got on top of the bowlers.
Smith followed up his 183 in the second innings of the drawn third Test in Cape Town with his 20th Test century and his sixth against England.
He had to work hard on Thursday evening and again on Friday morning and it took him 105 balls to reach his fifty. But with Amla providing reliable support, he picked up his scoring rate as he moved to a century off 182 balls when he cut Ryan Sidebottom for his 16th boundary.
England first innings 180
(D Steyn 5-51)
South Africa first innings
G Smith c Strauss b Sidebottom 105
A Prince c Swann b Broad 19
H Amla not out 73
J Kallis not out 7
TOTAL: (for 2 wickets) 215
Fall of wickets: 1-36, 2-201
Still to bat: AB de Villiers, JP Duminy, M Boucher, R McLaren, D Steyn, M Morkel, W Parnell.
But he got a good ball from Sidebottom five balls later, edging a seaming ball from the left-armer to Andrew Strauss at first slip.
Two overs later rain started to fall and within minutes there were large pools of water on the ground, halting South Africa's push for a win which they need to square the series.
Smith survived a confident appeal for a catch behind the wicket when he was on 15 in the fourth over of the day.
He chased a wide delivery from Sidebottom and the slips cordon went up in unison as wicketkeeper Matt Prior caught the ball but the South African captain was given not out by umpire Tony Hill.
England asked for a review and although a sound could be heard on television replays, third umpire Daryl Harper could not find a reason to overturn Hill's decision. The "snicko" and "hot spot" technology is not being used in the series.
Ashwell Prince was out in the next over, caught at second slip by Graeme Swann off Stuart Broad, but England could not make another breakthrough.
Both Smith and Amla played some streaky shots early on but the scoring rate was reasonably brisk, with England setting attacking fields.
But Smith and Amla started to bat confidently as they notched a fifty partnership off 81 balls and made the stand worth 100 after 156 balls. When Smith was out they had put on 165 off 245 balls.