Graeme Smith continued to give England a one-man drubbing as he completed his second double hundred in consecutive Tests at Lord's.
South Africa ended a shortened second day on 412 for two, giving them a 239-run first-innings lead.
Smith, who made 277 and 85 in the first Test, finished on 214 not out, having hit 29 fours and batted for seven and three-quarter hours.
Fellow left-hander Gary Kirsten scored a century during a second-wicket partnership of 257.
Smith kept shredding the record books until bad light ended play 18 overs short.
Only three men -- Don Bradman (three times), Walter Hammond and Vinod Kambli -- have previously hit double hundreds in consecutive matches.
Smith's was the fourth equal highest score made at Lord's in Test history, and no South African has ever scored more double centuries in their career.
The 22-year-old Smith, in only his 17th innings, now boasts three, equalling Kirsten's mark. All three of Smith's doubles have been scored well within a year.
The left-hander, with his broad bat and relentless determination, made a nonsense of England's young pace attack on Friday.
He clipped strike bowler James Anderson's second ball off the leg stump for four to the vacant fine-leg boundary. Next over, Steve Harmison offered him a short, wide ball first up which Smith cut for another boundary.
The 21-year-old Anderson, frustrated with his own lack of direction, soon fielded off his own bowling and shied wildly at the stumps, almost hitting Kirsten and prompting an angry reaction from Smith.
Nasser Hussain, who quit as England captain after the first Test, waded into the exchange with a few choice words of his own.
Kirsten, on 54, edged Andrew Flintoff to second slip where Mark Butcher juggled and dropped the catch. Moments later, it was Kirsten who repeated the shot, the ball this time falling just short of Butcher.
Smith kept flicking away in a leg-side arc between midwicket and fine leg. Occasionally there was a drive or a cut. There was rarely much drama about his unfussy approach.
On 98, there was a suggestion of a chance when he pulled Anderson to short midwicket where Marcus Trescothick failed to scoop up the ball.
England's failings apart, Smith's performance was one of real character. When he walked off, shortly after Kirsten had played on for 108 to Anthony McGrath's occasional medium pace, he received a standing ovation from the Lord's members.