Cook century powers Proteas in PE

Opener Stephen Cook made his second century in two Tests and South Africa built a hefty 432-run lead over Sri Lanka by the end of day three of the first Test in Port Elizabeth.

Cook was out for 117 but South Africa moved on to 5-351 in their second innings for a big advantage after the teams tussled for superiority over the first two days at St. George's Park.

Cook's century, his third in seven Tests since making his debut at the beginning of the year aged 33, came after his second century opening stand of the game with Dean Elgar (52).

They put on 116 for the first wicket, and Cook then combined with Hashim Amla for a 105-run stand.

Captain Faf du Plessis was 41 not out and Quinton de Kock undefeated on 42 in an unbroken 74-run partnership at stumps.

Part-time spinner Dhananjaya de Silva took 2-74 for Sri Lanka but the tourists are on the back foot again in South Africa, where they have never won a series and only won one of 11 Tests over the last 18 years.

Cook had to wait 15 years to be selected to play for South Africa.

He made a hundred on his debut against England in January, and another century on tour in Australia last month, although between those two highs there was a slight slump.

He also faced criticism for an unorthodox technique that some said wouldn't get him too far in Test cricket despite a long and successful first-class career.

"Shutting out the noise, that's always the challenge for a cricketer," Cook said.

"Whether it's the noise on the field from the opposition or it's from outside forces. I suppose it takes a bit of a thick skin and I've developed that over the years."

On Wednesday, Cook used his mechanical style to wear down Sri Lanka's bowlers on a pitch in Port Elizabeth that had been very helpful to the seamers on the first two days.

Cook hit 11 fours in all and set up South Africa's push for victory.

Alongside Cook's personal milestone, it was only the 10th time that the same opening pair has made a century stand in both innings of a game.

Cook ultimately went to an edge behind off Dushmantha Chameera, although Sri Lanka's frontline quick bowlers - Chameera, Suranga Lakmal and Nuwan Pradeep - had just one wicket each to go with the two from de Silva.

Lakmal, who took five in the first innings, had earlier removed Elgar, who tried to attack after passing 50 and lobbed a catch to mid-wicket.

Amla was out leg before to Pradeep for 48, two runs short of what would have been a welcome first half-century in eight Test innings for South Africa's leading batsman.

Amla hasn't reached 50 in Test cricket since August, and hasn't made a century since January.

He was trapped on what turned out to be the last ball before tea. Amla's dismissal was the 10,000th lbw in Test cricket history.

But he and Dean Elgar were seldom troubled after that as they improved their side’s lead before the stoppage.

South Africa: Faf du Plessis (captain), Stephen Cook, Dean Elgar, Hashim Amla, JP Duminy, Temba Bavuma, Quinton de Kock (wicketkeeper), Vernon Philander, Keshav Maharaj, Kyle Abbott, Kagiso Rabada.

Sri Lanka: Angelo Mathews (captain), Kaushal Silva, Dimuth Karunaratne, Kusal Perera, Kusal Mendis, Dinesh Chandimal (wicketkeeper), Dhananjaya de Silva, Rangana Herath, Dushmantha Chameera, Suranga Lakmal, Nuwan Pradeep.