The topic of transformation has been a central theme to this Test with Makhaya Ntini notching up his 100th appearance, but he is not the only member of South Africa's team to represent the modern-day diversity of the side. Hashim Amla, like Ntini, broke new ground when he became the first player of Indian descent to represent his country, and now - like Ntini - he has evolved into a pivotal figure within the team.

He is a convergence of two batting styles. The Indian in him is easy to see when he plays through the leg side - as he did to reach his hundred with a wristy whip through midwicket - and when he opens the face through the covers. The South African element comes through a determination never to yield, and a resistance to anything too flamboyant.

That cultural blend proved the perfect mix for South Africa as they attempted to prevent a full-blown collapse after England made significant early inroads. "There's no joke about it, we were under massive pressure," Amla said. "If we had a lost a few more quick wickets the total would have been considerably less."

Amla's first opportunity in the Test side came too soon, like a number of his contemporaries whose chances came for reasons beyond pure cricket. But unlike some who have drifted off the scene - such as Thami Tsolekile, the wicketkeeper who made his debut in the same series against India in 2004, and whom England faced at Port Elizabeth in their opening Test five years ago - Amla's second coming as an international cricketer has taken him to new heights.

In 2004-05, England classed him as a walking wicket and the statistics backed up that assessment as Amla played only two of the five Tests and averaged nine. Even in 2008, when he toured England and batted at No.3, they weren't convinced about his technique. During the recent one-day series, when he replaced the injured Jacques Kallis, they targeting him with a short-pitched attack and more of the same was expected in the Tests. However, the slowness of the Centurion wicket has precluded such a ploy, and that has suited Amla down to the ground.

Nevertheless, Amla still needed a partner to steer South Africa from their unstable 46 for 4 - a precarious lead of 108 - and in AB de Villiers he found the ideal ally. While Amla calmly worked the gaps, de Villiers carried the fight back to an England attack that was sensing its chance for a kill.

There was clear intent from de Villiers not to let Graeme Swann settle into another probing spell of offspin. From his third ball against Swann (and ninth of his innings) de Villiers skipped down the pitch and deposited him into the stands over long-on. Swann was brave enough to toss the next one up as well, but de Villiers was happy to defend. He had made his point.

The partnership between Amla and de Villiers was the latest momentum shift of a fluctuating match and it could prove the decisive one. When de Villiers departed to Stuart Broad, driving a fraction early at a slower ball, the lead was a far more comfortable 227 on a surface that, while not proving unplayable by any means, was difficult to score quickly on.

"I expected a lot more up-and-down bounce," Amla said. "Once the ball got old it didn't seem to react as much and we expected a little more. I think it probably played the best out of the four days, because when the ball got old, there wasn't as much variable bounce, but let's hope tomorrow has the most variable bounce."

Mark Boucher played a typically forthright innings, but he was able to bat in such a positive manner because of the hard yards put in by de Villiers and Amla. "There was a bit of pressure but fortunately myself and AB got a partnership going and it set the platform for Boucher to come in and take the score up," Amla said.

The ball that finally removed Amla, a true shooter from James Anderson, will have sent shockwaves through the England dressing room, and Amla was happy to take one for the team. "Although I may have been extremely disappointed to get out there were a few guys in our changing room who said 'sorry Hash, but it's good news'. We've got to hope that the wicket is a bit more up-and-down so it makes it a little easier for us."

South Africa have always had their noses in front during the game, but now they are a couple of lengths clear. And after the day that Amla has enjoyed, wouldn't it be fitting if the final chapter of this match belonged to Ntini.