How careers can turn on small moments. Few batsmen have achieved so much so early as Alastair Cook. Only two players in history have scored more runs at a younger age and no England cricketer comes within a year of having done so.
Yet when he went to the crease yesterday morning at 25 years and three days old, it was as a grizzled veteran of 50 Test matches playing for his future. Failure would not have meant immediate withdrawal of his place as an England opening batsman, but it would have made the scrutiny and the search for an alternative more intense.
For an hour, Cook was painful to watch. He was patient, vigilant and assiduous but there was the unmistakeable stench of fear about his work. He left the ball more often than he played it; South Africa were willing him to try something more adventurous or foolhardy; he resisted.
Could he, South Africa must have been asking (and were probably posing the question of Cook as well) be embarrassed out? From the first 37 balls he faced he added a mere single to his overnight 31. It had been nine short innings since his last Test 50.
But Cook survived to prosper. His 10th Test hundred placed England in a commanding position on the third day of the second Test and he was well into his seventh hour at the crease when he edged one, typically, to second slip.
Cook shared a long and important partnership with Paul Collingwood which gave England space to breathe and Ian Bell emerged to embellish their platform with some ornate furnishing. By the close, England led by 43 runs with five wickets in hand.
For the most part on another anodyne pitch, South Africa's attack lacked guile and menace. The wind hardly helped their spinner, Paul Harris, and though Makhaya Ntini came back well from the brief but harsh walloping he received the previous day, he rarely threatened. Only Dale Steyn, who went wicketless, and Morne Morkel, approached menacing.
The single defining moment of Cook's innings and the rest of his batting life may have arrived when he was on 64. He was out of the woods but hardly on the sunlit uplands when he was adjudged to have been caught at short leg.
It was the sort of decision that might have been given not out on another day, the sort to persuade umpires to seek different occupations. Amiesh Saheba erred on the side of raising his finger. Under the new regulations Cook was entitled to ask for a review of the verdict and he was duly given a stay of execution.
The ball had missed the edge of the bat on the way through and the gloves as it rebounded. Justice was done. The reprieve meant that Cook was able to help the tourists establish a position of strength on a ground where they have not lost since 1928.
The loss of their opener then would have put England in peril, not least because it would have brought in another out of form batsman in Ian Bell. Jonathan Trott went in the second over of the day after he received a peach from Morkel which lifted, held its own and took the edge.
Kevin Pietersen then batted beautifully for an hour, his dominance probably enhanced by Cook's scratchiness at the other end. If he had not been rapturously received at the ground where he began his professional career, he was greeted with polite applause.
This was a sign that Pietersen is English now, all right. He played a few scintillating strokes but was given a warning when he was put down at slip by Jacques Kallis, attempting to force a quicker ball from Harris.
But he ignored it and was stone dead leg before 11 runs later when essaying a sweep against the most underrated bowler in world cricket. England had some regrouping to do and in Collingwood they had the man to help Cook do it.
They shared a careful stand of 142 for the fourth wicket, Cook growing in stature, Collingwood playing like a man in form. Cook reached his 10th hundred with a clip for two wide of mid-wicket and Collingwood arrived sedately at his 18th Test fifty.
Between lunch and tea, they added 91 in 28 overs. Cook was out shortly afterwards, caught low at second slip, a place where his downfall has been caused so many times before. But his doggedness and calmness had made a point, they had made several points.
After Collingwood was out, clearly tiring on a hot day, albeit against a labouring attack, Bell was much more pleasing to the eye. The manner in which he hoisted Harris effortlessly for six bespoke a class act. England are on top, the draw remains favourite but Cook is back and Bell is on the way.
Durban (Third day of five) England lead South Africa by 43 runs with five first-innings wickets remaining
South Africa won toss
SOUTH AFRICA First Innings 343 (Smith 75, Kallis 75, De Villiers 50; G Swann 4-110)
ENGLAND First Innings
Overnight: 103-1 (Strauss 54)
*A J Strauss b Morkel......... 54
67 balls 9 fours
A N Cook c de Villiers b Morkel......... 118
263 balls 11 fours
I J L Trott c Boucher b Morkel......... 18
31 balls 2 fours
K P Pietersen lbw b Harris......... 31
52 balls 4 fours
P D Collingwood c Boucher b Duminy......... 91
215 balls 7 fours
I R Bell not out......... 55
84 balls 5 fours 1 six
†M J Prior not out......... 11
27 balls 2 fours
Extras (lb 4, w 3, nb 1)......... 8
Total (5 wkts, 123 overs)......... 386
Fall: 1-71 (Strauss), 2-104 (Trott), 3-155 (Pietersen), 4-297 (Cook), 5-365 (Collingwood).
To bat: S C J Broad, G P Swann, J M Anderson, G Onions.
Bowling: Steyn 26-6-60-0 (3-0-8-0, 1-0-4-0, 3-0-16-0, 6-4-5-0, 4-2-7-0, 8-0-19-0, 1-0-1-0), Ntini 20-3-79-0 (3-0-25-0, 6-2-8-0, 4-0-15-0, 1-0-5-0, 6-1-26-0), Morkel 27-6-69-3 (w3) (9-3-22-1, 3-1-7-1, 6-1-20-0, 2-0-3-0, 6-1-13-1, 1-0-4-0), Kallis 14-1-43-0 (nb1) (2-0-12-0, 3-0-12-0, 3-0-5-0, 6-1-14-0), Harris 23-2-92-1 (1-0-1-0, 3-0-13-0, 7-0-31-1, 3-0-18-0, 3-0-10-0, 6-2-19-0), Duminy 13-1-39-1 (6-1-13-0, 2-0-10-0, 5-0-16-1).
Progress: Third day: 150: 46.1 overs, Lunch: 190-3 (Cook 75, Collingwood 9) 60.0 overs, 200: 64.4 overs, 250: 78.2 overs, Tea: 281-3 (Cook 115, Collingwood 59) 88.0 overs, 300: 93.4 overs, 350: 110.3 overs, Close: 386-5 (Bell 55, Prior 11) 123.0 overs. Cook 50: 136 balls, 5 fours. Cook 100: 218 balls, 10 fours. Collingwood 50: 106 balls, 4 fours. Bell 50: 65 balls, 5 fours, 1 six.
Umpires: Aleem Dar (Pak) & A M Saheba (India).
TV replay umpire: S J Davis (Aus).
Match referee: J D Cloete (Sri Lanka).
Turning points How the action unfolded on day three
*9.35am Plaudits for Pietersen
Pietersen walks out for his Test match at his home ground and his 100th innings for England to, perhaps surprisingly, a warm round of applause.
*10.35am Cook releases the gas
Cook scores two runs, having taken a single from his first 37 balls of the day.*11.01am
Pietersen, having been dropped on 20, is leg before to Paul Harris sweeping.
*11.35am Appealing time
Cook, on 64, asks for review after being given out caught at short leg and his appeal is successful. The sort of moment on which careers turn.
*1.35pm Century clip
Cook reaches his 10th Test hundred, with a clip wide of midwicket for two.
*3.50pm Charmed Collingwood
Collingwood, in a fallow period is lucky to escape a chance offered to deep square leg off Morkel.
*4.29pm England in front
England take lead with Bell single.
*5.04pm Prior escape
Matt Prior dropped at short leg by Hashim Amla.
*5.30pm Cruise to control
The match's first full day ends with England 43 ahead after 123 overs.