England look set to complete a 3-1 series win in South Africa after turning the screw on the third day of the Johannesburg Test. Where have they improved over the course of this tour?
The top order
At the time Rory Burns went home from this tour, there were serious concerns about the strength of England's top order. That was understandable, too: Dom Sibley had a Test average of 14.20 and Zak Crawley had one Test run.
But the pair have taken the opportunity offered so well that they have both made a strong case for retention for England's upcoming series in Sri Lanka and beyond. In Johannesburg, they not only recorded England's first century opening stand since December 2016, but became the first England opening pair to record two 50+ stands in a game since 2012. They also became the first England openers to register three successive 50+ stands since that year.
Sibley has been the heavier scorer of the two. With a maiden century in Cape Town to go alongside scores of 29, 34, 36, 44, 44 he has become the highest run-scorer in the England side (and the top four of either side) and joined a distinguished list of England openers - Geoff Boycott, Graham Gooch, Michael Atherton, Alec Stewart, Michael Vaughan, Marcus Trescothick, Andrew Strauss and Alastair Cook - to have made six consecutive 25+ scores in Test cricket in the last 50 years.
While Crawley managed only one half-century, he did improve his career-best score for five successive innings - which underlines the sense of his coming to grips with the challenge by the day - and looked ever more comfortable. Together, they regularly saw the shine off the ball, tired the South Africa attack and eased the way for the batsmen that followed.
With Burns expected back from injury in time for the first Test of the English summer in June, England could be left with some tricky selection decisions. Realistically, however, they may decide to field all three players with Joe Denly squeezed out. Either way, from a position where England had holes in the top order, they now appear to have options. That represents significant progress.
Seam-bowling strength
Not so long ago, the loss of James Anderson to this England attack would have been catastrophic. And, had you been told at the start of the tour that England would win the series, you would have presumed that Jofra Archer would have been in the thick of things. As it is, Anderson has missed two Tests and Archer three, yet England have taken 20 wickets for three Tests in a row and may well do so for a fourth.
That's not to say Archer and Anderson have been irrelevant. Both claimed five-wicket hauls in the early part of the series. But the fact is, England have found other bowlers - notably Mark Wood - who have combined to form an effective attack. Ahead of South Africa's final innings of the series, Stuart Broad (with 12 wickets) was England's top wicket-taker of the series, with Sam Curran two behind. With Ben Stokes, who delivered the match-clinching spell in Cape Town, in reserve, England look as if they have some depth in the seam-bowling department.
Wood was, no doubt, the stand-out performer. He impressed with his pace at Port Elizabeth without gaining the wickets to show for it, but demonstrated his improved fitness by declaring himself available for the following Test in Johannesburg, bowling every bit as quickly and claiming a five-wicket haul. It underlined the impression that he is a different, more robust and quicker bowler since he lengthened his run-up at the end of 2018. In the three Tests he has played since, he has claimed two five-wicket hauls and taken his wickets at an average of 14.42. It hasn't felt aberrational, either.
The prospect of Wood and Archer in tandem remains mouthwatering from an England perspective, and seems to alleviate some of the concerns about Broad and Anderson coming towards the end of their careers. Somewhere in there is the nucleus of an attack that could - just could - enjoy some success in Australia (and perhaps even India) over the next couple of winters.
Spin department
A few months ago, Dom Bess was unable to secure a place in his county side. Dismayed at how his international prospects seemed to have melted away since a brief appearance on the Test stage in 2018, he was told to take a break from the game to freshen his head at the end of the season.
But then came a lifeline. The ECB invited him on a spin camp to Mumbai where, among other people, he worked with former Sri Lanka spinner Rangana Herath. So rapid was the improvement, he put himself in position to be called into the Test squad as backup after Jack Leach became ill. And, arriving on tour to find Matt Parkinson struggling with his red-ball game, Bess soon leapfrogged him and came back into the Test side for the Cape Town Test.
He performed well, too. While he managed only two wickets in the match, he performed an excellent holding role - he conceded just 1.98 runs per over throughout the match - to allow England's seamers to rest and rotate. Better followed when he claimed a maiden five-wicket haul to unlock a slow wicket in Port Elizabeth and show that he now had the skills - the control, the variation and the mentality - to perform a valuable function in most circumstances.
None of this means he is established as England's first-choice spinner. But with Moeen Ali's Test future uncertain and Leach apparently facing something of a fight to regain full fitness ahead of the Sri Lanka tour, Bess' re-emergence has provided some peace of mind for England. He's 22, with some ability with the bat; he could develop into a very useful player.
A settled middle order
The emergence of Ollie Pope - who most agree is the most promising batsman England have produced since Joe Root - has given England's middle order an imposing look. With Root at No. 4, Stokes at No. 5 and Pope to follow, England have players with the ability to rebuild or accelerate as the situation requires.
Stokes' development as a batsman may be under-appreciated. He is averaging 54.26 since the start of February 2019 and, while his reputation as an aggressive hitter is well-earned, has shown he can also defend for long periods and build an innings in traditional fashion. We saw both sides of his game this series: a brisk 72 in Cape Town (it took 47 balls) helped set up the declaration, while his century in Port Elizabeth came at a more conventional tempo. On both occasions, he played the innings his side required.
Pope has been the real revelation, though. While he has long been recognised as an outstanding talent, he has now started to fulfil the bold predictions made for him. After masterfully shepherding the tail in the first innings in Cape Town, he produced a high-class maiden century in Port Elizabeth and followed it with another final half-century in Johannesburg. Few would bet against him flourishing in Test cricket for a decade or more.
Again, it looks like the sort of middle order that could prosper in both India and Australia over the next couple of winter. It looks like progress.
Consistency
This England side has produced some excellent performances over the last few years. But what they've rarely hinted at is consistency. So, after the triumph of winning in Sri Lanka, they were heavily beaten in the Caribbean. And, after losing in Manchester, they hit back with victory at The Oval. You rarely know what you're going to get from them.
But here, at last, they started to show some consistency. Not only have they taken 20 wickets in the first three Tests - they're on course to do it in the fourth, too - but, when they reached 400 in the first innings in Johannesburg, it was the first time since March 2013 they had made 400 in two successive innings. They had declared on 391 in their second innings in Cape Town, too.
Central to this has been the performance of the young opening pair. But the likes of Denly and that strong middle order have contributed, too. Increasingly, they have embraced a relatively old-fashioned approach to their batting - seeing off the new ball and taking their time to build substantial innings - that has been somewhat in contrast to the method of the previous regime.
It does have to be acknowledged their opponents, South Africa, are in something of a transitional state. But there are signs of progress in this England side and, with a year before the India tour and two before the next Ashes, there is renewed hope they may be able to mount a decent challenge.