I've developed a thick skin - Cook

'We had urgency about us today' - Stephen Cook (2:13)

South Africa opener Stephen Cook talks after scoring his third Test hundred in the ongoing Test against Sri Lanka (2:13)

Stephen Cook has had bigger innings under more pressure than he did at St George's Park on Wednesday but there may not be a knock more significant in the context of his career. After a century in Adelaide in South Africa's previous Test and a fifty in the first innings, Cook wanted to show consistency, especially as an answer to the questions over who will face the chop when AB de Villiers returns.

"Shutting out the noise is the challenge of a cricketer, whether it's the noise on the field from the opposition or what's being said off it," Cook said. "It takes a bit of a thick skin and I've developed that. I've been in a lot of different change-rooms and pretty hostile environments. I always say that if you make it out of your own dressing room, you can make it in the middle."

Cook's domestic change-room included Neil McKenzie, his current batting coach. Both have former cricketers as fathers and both come from what Cook calls "the school of tough love". One example of a lesson Jimmy Cook passed down to Stephen is: you can get out for any reason except being tired. So, between his dad and McKenzie, Cook has had a double dose of drilling in the importance of taking his chance and he disappointed neither.

By his own admission, this innings was less intense than those of the recent past and it gave him the chance to show what he can do without much angst about the opposition. "Australia was very tough and I spoke about the hardships I had there," he said. "Not that it's easier now - because Test cricket is Test cricket - but I was a bit more relaxed in this Test match. I was coming off a hundred and feeling a bit better about how things are going."

With South Africa in a strong position before Cook's innings even started, he could concentrate on "implementing the few small changes" he had made between the Australia series and this one. The only noticeable tweak was the increased strike rate, which was part of South Africa's plan to set up the declaration. They have not decided exactly when it will come but with a 432-run lead, it cannot be too far away.

"We had an urgency about us today, especially in the way we ran," Cook said. "In the first innings Sri Lanka employed that deep point, deep-square leg tactic quite a lot to cut off the boundaries. But Dean and I, and when Hashim came in, we looked to exploit the singles and make sure they couldn't settle on their lengths. We didn't hit that many more boundaries today but we rotated the strike and ran a lot harder. That allowed us to stay ahead of the game."

Cook shared century stands with Elgar and Amla, each notable for their own reason. While Cook and Amla scored at the fastest rate in the match - 5.57 - Cook and Elgar's stand made them only the 10th pair in Test history to post century opening partnerships twice in a match. Before this Test, they had not even put on fifty together. Now, they look like they have planted the seeds that could bear fruit in future.

"It was very nice to bat with Dean for a period of time. So far, we've dovetailed and one of us has scored runs and one hasn't but opening the batting has always been about forging a partnership and the only way you get that partnership is by spending time out there," Cook said.