Amla remains firm in tight contest
South Africa 309 and 145 for 3 (Amla 57*, Steyn 0*) lead England 315 (Bairstow 95, Bell 58, Morkel 4-80, Steyn 4-94) by 139 runs
Scorecard and ball-by-ball details
This was an unforgiving day of Test cricket: unforgiving for Jonny Bairstow as he fell five runs short of a deserved maiden Test century, unforgiving for Jacques Kallis as two decisions he will rue for a lifetime continued his poor Lord's record in what could be his last Test on this ground and unforgiving for England's bowlers as the combination of a docile surface and sweltering heat made their task of bowling out South Africa a second time doubly difficult.
In such taxing circumstances, with the title of the world's best Test side at stake, South Africa and England are scrapping to the last. It has been a wonderful Test, slow at times but immensely combative and benefiting from the sense that something important is at stake. At the close of the third day, South Africa held a lead of 139 runs, with seven wickets remaining. They bat long and because of the extra cutting edge of their attack feel a touch ahead of the game, but the job is far from done.
A rag-tag of an English cricketing summer, ruined by poor planning and even poorer weather, is reaching a marvellous climax, played out before expectant, thoroughly contented capacity crowds.
Matt Prior, England's wicketkeeper, will also have cause to reflect on cricket's unforgiving nature. He dropped Hashim Amla when he was 2, a spring down the leg side and a full glove as he glanced Stuart Broad. Amla reached his half-century with a straight drive in the final over of the day and his blissful cover drive against Broad off the penultimate ball of the day reminded England that here was a player who could take the game away from them very quickly.
But England have removed Kallis, lbw to Steve Finn. He was convinced that he got a thin inside edge and referred umpire Simon Taufel's decision immediately, but technology discovered only ricochets against pads and the verdict was upheld. In the first innings he fell victim to what can only be described as a brainstorm by the third umpire, Rod Tucker, so his frustration was understandable. England's delight at his removal knew few bounds.
South Africa have also lost their indomitable captain, Graeme Smith, lbw on the sweep to Graeme Swann. England's plots to dismiss have foundered in this and every previous series and he grimaced and growled and worked the ball through the leg side with the immense determination of a man who sensed that his long-awaited ambition - the rise of South Africa to No 1 in the Test rankings - was nigh. But this time, Swann's strengthening of the leg side and encouragement of the sweep to break the stranglehold - not one of Smith's strengths - worked a treat.
Swann was pitted against South Africa batsmen who by and large have played him with supreme confidence, but three raucous lbw appeals in one over as Kallis and Amla built their stand of 81 showed that he was capable of fighting back.
England were so desperate to remove Smith that earlier they gambled wildly - and lost - on a referral for a catch at the wicket. The ball from Swann turned sharply and with more hot weather forecast spin could come to the fore in the last two days. So could reverse swing - and Broad found a little of it to have Alviro Petersen lbw.
England's tail-enders withstood a barrage of short-pitched bowling from Dale Steyn (also struck painfully on the left-hand himself when acting as a nightwatchman shortly before the close) to steal a lead of six runs on first innings.
England added another 107 after beginning the third day on 208 for 5. The match situation was pressure enough for Bairstow, as was the fact that he owed his place to England's stand-off with Kevin Pietersen, and the relentlessness of South Africa's attack added to it.
South Africa's fast bowlers first squeezed him dry and then silenced him, Morne Morkel striking his middle stump 20 minutes before lunch to leave England looking on in anguish. He made 95 from 196 balls and produced an innings of pluck and craft in the most challenging of circumstances. He has an easy manner, a deft, enterprising approach and in his late father, Bluey, follows one of the most popular Yorkshire cricketers who ever lived.
South Africa had adjusted their thinking against Bairstow overnight. Gone were the short balls with which they had peppered him the previous day in recognition of his troubled introduction to Test cricket against the West Indies quick Kemar Roach. Morkel's final delivery to him was in keeping with their adjusted approach, fast and fullish, and Bairstow, searching for his favourite leg-side, was found wanting.
England lost Prior and Broad to the second new ball and Bairstow, his responsibilities weighing heavily, managed only one run in the last 40 minutes before his middle stump tumbled and his captain, Andrew Strauss, on the Lord's balcony, held his hands to his face in disappointment.
He had reached 90 with a clip through mid wicket off Vernon Philander, his best moment of the morning, but his next boundary was a thick edge wide of the slips and, on 95, two indecisive wafts at short and wide deliveries from Morkel illustrated his tension.
That Prior and Bairstow were still around when the second new ball was taken nine overs into the morning was to England's advantage, but the advantage only lasted one ball. The first ball, from Philander, curled away from Prior and he obligingly chased it, as if transfixed by its newness, and edged to second slip.
Broad bats these days as if he has not been to the crease for years and, trying to shovel Steyn off his body, popped up a catch to Amla at short leg. Swann, on 12, successfully overturned Steyn's lbw decision and, although Steyn returned with fresh fervour after lunch - hitting Anderson on the elbow before bouncing him out and Finn on the helmet - a spirited last-wicket romp of 32 gave England a crowd-cheering first-innings lead.
David Hopps is the UK editor of ESPNcricinfo