Five series takeaways for England's T20 World Cup preparations

Their seamers were impressive at the death, but England bowled poorly up front throughout, becoming the fifth team to take only one Powerplay wicket in a T20I series of three or more games and leaking 11.16 runs per over in the phase. Moeen Ali bowled seven overs with the fielding restrictions in place - Morgan explained that as an analytics-inspired move aimed to target Quinton de Kock's relative weakness against offspin - and took the only wicket, but Tom Curran, Chris Jordan and Mark Wood all leaked runs early on.

There is a particular premium on early wickets: not only do they typically result in the cheap dismissal of one of the best opposition batsmen, but they also mean that middle-order players come in with less freedom to attack. While South Africa's lack of batting depth meant that was not particularly costly in this series, it will be a cause for concern with knockout T20 World Cup games in mind.

While the return of Jofra Archer should help matters, England might also consider picking a seamer specifically for their skill with the new ball. As the numbers show, forgotten man David Willey has the best recent international record in that phase, while Saqib Mahmood presents an alternative option.

The debate about Jos Buttler's best batting position will rumble on right through until the World Cup in October, with pundits increasingly falling into one of two camps: those who think he should face as many balls as possible, and therefore open the batting; and those who reason that England lack a batsman in the Andre Russell mould who can close out an innings with destructive late hitting, so Buttler should go down the order to fill that gap.

Buttler's efforts in the series give little clarity as to what the right answer is - there has never been any doubt about his skill, after all - but the efforts of their lower-middle order suggest that Morgan's conviction that Buttler should open is well-placed.

While they failed to kill the first game at East London when they should have, England benefitted from imperious late-innings hitting from Moeen and Morgan in the second and third T20Is respectively, and the two have been in superb form over the last year. Much as Moeen's real strength lies in taking down spinners in the middle overs, he is still belligerent at the death, while Morgan has cast aside any doubts about his ability with a stunning run in T20 cricket since the conclusion of the 50-over World Cup.

Nobody has scored faster at the death (16th-20th overs) than Morgan since the start of last year, with Moeen slotting in close behind. While they have largely played in good batting conditions, their records are both superb. In eight T20Is since deciding to stay on as captain following the World Cup, Morgan averages 54.66 while striking at 183.24, putting any doubts about his place firmly to bed.

While the match situation dictated constant aggression in the final game of the series, England struggled to score freely in the middle overs in the first two T20Is: at East London and Durban, they scored at 7.55 runs per over between the end of the Powerplay and the start of the 16th over, compared to 10.25 in the first six and 12.10 in the last five.

Perhaps surprisingly, the most culpable batsmen were Jason Roy (whose strike rate dropped from 194.33 in the Powerplay to 135.33 in the middle) and Morgan (113.33 in the middle, 215.33 at the death).

The third game of the series, in which Jonny Bairstow took down Tabraiz Shamsi and Bjorn Fortuin, offered something of a template, and highlighted Bairstow's value attacking spinners; while Morgan and Roy had been willing to tick over with singles in the first two games, leading to a post-Powerplay lull, Bairstow's intent kept England surging.

England's use of Joe Denly in their T20I side has been bizarre in the last two years: across his 206-match T20 career, his only innings outside of the top four have been his first two appearances for Kent (in 2004 and 2006) and his last six games in an England shirt. Innings of 3 and 1 in this series could be his last, with the upshot that there is a middle-order vacancy.

Dawid Malan, the other backup batsman, struggled against Shamsi at Centurion, and England have no shortage of options as to how to fill Denly's spot: they could move Buttler down and slot in another opener, play a specialist middle-order batsman like Dan Lawrence or Delray Rawlins, or push Moeen or Stokes up and pick a specialist finisher or an extra bowling option. They have the depth to choose any one of those options and find a way to make it work, but with only nine T20Is scheduled before the World Cup, they need to take a call sooner rather than later.

England themselves have only a small number of games remaining before the World Cup, but T20 is unique in the sheer number of games that contenders will play before they finalise their squad for the tournament.

In the run-up to the 50-over World Cup, fringe players could hope for a handful of England Lions games and between eight and 11 Royal London Cup fixtures per year in which to prove themselves in the format, but this year they could well be available for more than 30 short-format matches.

To take Tom Banton as an example, he travels to Pakistan this week for the PSL following a Big Bash stint this winter, then goes to the IPL for two months, before coming straight back into the Blast for Somerset and then into the Hundred for Welsh Fire. By the end of that run of fixtures, it is perfectly feasible that someone not currently in the conversation could present a compelling case for inclusion.