Ben Stokes hammered a six out of the ground as he made up for lost time with a century on a rain-hit second morning at St. George's Park.
Returning to the crease on day two after the start was put back by 45 minutes, Stokes and Ollie Pope kicked on after easing fears of another England batting collapse in the third session of Thursday's first day.
Joe Root's wicket left England 148-4 on the opening day, but Stokes and Pope clocked up an unbeaten 150 partnership as both impressed on the second morning.
Stokes looked to kick on after passing 50 as he twice slapped Keshav Maharaj over the rope, with the second clearing the stadium fence and bouncing off down the road before being retrieved by someone who had hopped the fence.
As the partnership pushed England into a commanding position before lunch, Stokes moved past 4,000 Test runs before clocking up his ninth Test ton moments later.
News that Kagiso Rabada has been handed his fourth demerit point over a two-year period and thus ruled out of the final Test served a further blow to the hosts on the second morning.
His overzealous celebration following the wicket of Joe Root on Thursday also cost Rabada 15 per cent of his match fee.
Standard Sport's Will Macpherson in Port Elizabeth said: "There’s been a slightly somnolent feel at St George’s Park this morning, with the rain and the news of Kagiso Rabada’s ban."
"No one told Ben Stokes, though, who seemed to determined to launch into South Africa’s bowling. His second six off Keshav Maharaj sailed 30 metres over a long boundary and out of the ground, to the crowd’s disbelief. There was surprise and some mirth when the ball was relocated a couple of minutes later."
