At the beginning, when England lost the first Test and were being hit by injuries and illness, there was the danger of it turning into a shambles.

For them to turn it around and win 3-1 shows signs of really strong leadership. Not only is Root in complete control, but he is also batting well.

Things started to turn for him before England got to South Africa, during the second Test on the tour of New Zealand.

England had lost the first Test and there were mutterings around Root's position. Was he the right man to be skipper? Was the captaincy taking too much of a toll on his batting?

I have not asked him, so I do not know for sure, but I got the impression that he decided to enter the second match in Hamilton with a much more relaxed and upbeat attitude. It was just something I picked up by observing and interviewing him in the days beforehand.

Although England did not win, Root got a double hundred and the questions went away.

He actually started the tour of South Africa with what turned out to be his only mistake - asking South Africa to bat first in the opening Test at Centurion Park.

I understand why Root made that call - it probably would not have been his decision alone - but it was a strange one and England lost the match.

Since then, he has barely put a foot wrong.

It is easy to spot where he has improved, even in a short space of time. In New Zealand, for example, he bowled Jofra Archer into the ground. In South Africa, he looked to have a much greater grasp of how to use his fast bowlers - when to bowl them, from which end and for how long, and where to place the fielders.

More than anything else, England look like Root's team. If you were to watch them without knowing who was captain, it would not take long to work out it was Root, with the Yorkshireman buzzing about, speaking to players and directing traffic.

You might ask why this has taken so long. After all, Root was named captain three years ago.

There are a number of factors. Root, like Alastair Cook before him, has been learning on the job. England captains have so little chance to lead in county cricket. Root, for example, had taken charge of just four first-class matches before he was handed the England reins.

The timing of his ascent also was not ideal. In 2017, he had only one home summer before what turned out to be a difficult tour of Australia, after which England's focus shifted to their attempt at winning the World Cup.

He is also helped by the number of young players in the England side. For the majority of this tour, there has been no James Anderson or Jonny Bairstow, while Moeen Ali has been out of the side for some time now.

Instead, he has had Archer, Dom Sibley, Zak Crawley, Ollie Pope, Dom Bess and Sam Curran, all of whom are under the age of 25.

I am not for one second suggesting the experienced players are difficult to manage, but the younger players will be full of enthusiasm and wonder at the beginnings of their Test careers. They will look up to Root and hang on his every word.

Not only that, but Root has probably assumed more responsibility since the departure of former coach Trevor Bayliss.

Sometimes, when a coach is in place and a new captain takes over, as was the case when Root was made skipper, it is the coach who naturally assumes the more senior role.

When the roles are reversed and it is the coach who is the new appointment, the opposite can be true. That is probably what has happened here with arrival of Chris Silverwood. It also helps that Root and Silverwood know each other very well.

At the end of last summer, director of cricket Ashley Giles backed Root as the man to lead England to Australia at the end of 2021.

After England lost the first Test in New Zealand, perhaps that was not a certainty, but now you can see no reason why Root should not be captain down under, because the time invested in him is starting to pay off.

England's win in South Africa is only their second overseas success in four years

In addition, he has a young team who are showing the green shoots of progress. Sibley ended this series as England's second-highest run-scorer, Crawley displayed real promise and Bess had a couple of strong Tests. Pope seems bound for something special.

Looking ahead, the home international summer against West Indies and Pakistan will be reasonably low key, especially with the English domestic game gearing up for the arrival of The Hundred.

Maybe this will be the first period when Root can relax and actually enjoy being the England captain. He should, because the following two winters, in India and Australia, will be incredibly tough.

Before then, England will turn their immediate attention to white-ball matches against South Africa.

It actually might be quite emotional for the one-day side to play together again for the first time since winning the World Cup.

I expect them to beat South Africa in both that series and the Twenty20s, which will be used to prepare for the T20 World Cup in Australia in the autumn.

Not only that, but I suspect England will be working hard on Moeen, trying to persuade the off-spinner to end his Test hiatus and be available for the tour of Sri Lanka in March. They will certainly need him.