Suranga Lakmal took four wickets and gave Sri Lanka a slight edge on the first day of the first Test against South Africa at St George's Park Monday. Opening bowler Lakmal took four for 62 in 23 overs as South Africa reached 267 for six at the end of a day on which top scorer JP Duminy admitted the hosts had failed to capitalize on a century opening partnership between Stephen Cook and Dean Elgar. "It was a bold move to bat first on a pitch with a bit of grass on it," said Duminy, who made 63 before falling to left-arm spinner Rangana Herath. "The way Dean and Stephen started was exceptional. Unfortunately we didn't capitalize. Quite a few of us got starts but no-one got a hundred." Lakmal took the first three wickets and later dismissed South African captain Faf du Plessis. Herath took two for 48. When Du Plessis won the toss and decided to bat on a well-grassed but slow pitch, it was anticipated that the first two hours would be the most difficult for batsmen, with early life expected from moisture in the pitch. Cook (59) and Elgar (45) were seldom troubled as they reached 92 for no wicket at lunch. Any thoughts of a South Africa run feast in the afternoon were spoiled by Lakmal in a superb spell immediately after lunch. He was backed up well by Angelo Mathews and Nuwan Pradeep as only 13 runs were added in 10.2 overs for the loss of both openers. "Suranga bowled exceptionally well," said Sri Lankan batsman Kaushal Silva. "The first two hours didn't go our way. It was a bit slow and there wasn't much movement but we came back strongly. "Suranga stuck to his plans and that gave us the advantage after lunch. He bowled a good line and length and that got him the wickets." Cook was stuck on the crease as he edged a ball from Lakmal that seamed away from him, with wicketkeeper Dinesh Chandimal taking a good, low catch to end an opening stand of 104. Only one run was added off the next 29 balls before the left-handed Elgar pushed at a ball angled across him to present a second catch to Chandimal. Duminy threatened to swing the balance back to South Africa. The left-hander hit the first ball he faced from Lakmal through the covers for four and raced to 34 off the first 23 balls he faced, including eight fours. By contrast, Hashim Amla, who came in at No. 3, struggled to find his timing, scoring only 20 runs off 76 balls before Lakmal returned to the attack immediately after tea and had him caught behind. It was a continuation of a poor run of form by Amla, who scored only 98 runs at an average of 16.60 during South Africa's series victory in Australia last month. The dismissal meant that Amla's Test career average dipped below 50 for the first time in more than four years. But Duminy said Amla's cool head had been an important contributor to their third wicket stand of 73. "What helped was Hash at the other end reminding me that what happened the ball before doesn't matter, to concentrate on each ball," said Duminy. "He added a lot of value to my innings. We've all been through stages in our career where there's a lack of runs but he's a quality player and I've no doubt that a big hundred is just around the corner." Duminy lost his earlier fluency as the Sri Lankans altered their line to prevent his flow of off-side drives. He eventually lost patience and missed a sweep against Herath to be given out leg before wicket. He sought a review but umpire Bruce Oxenford's decision was shown to be correct. Duminy made 63 off 95 balls with ten fours. The Sri Lankans successfully reviewed a decision by Oxenford four overs later when Temba Bavuma went back to Herath and was originally given not out when he was struck on the pads.