It would be an extraordinary achievement if England became both Twenty20 and one-day-international world champions, considering not long ago they were known as being about 20 years behind the pace of limited-overs cricket.
To now suddenly be in this position, it shows how much hard work and how much focus on white-ball cricket has taken place in the last five to eight years.
Having managed to dismember South Africa reasonably easily, I would say England are favourites for the Twenty20 World Cup in India next year.
The tourists won all three games and became the number one T20 team in the world, I would be nit-picking a bit to find faults in their performances.
Malan's T20 brilliance and world-class Rashid
Dawid Malan confirmed what a brilliant player he is and the batsmen, by and large, all showed us what they are capable of doing, which is chasing down any target.
Every bowler in the world knows that any batsman in England's top six can take them apart and overcome virtually any total.
Having said that, South Africa's tactics against Jason Roy were effective, bringing on left-arm spinner George Linde to bowl the first over.
When he is playing at his best, Roy is incredibly still and hits the ball in straight places with huge movements, but the spinner got to him a bit.
It seemed to disrupt his rhythm of batting and he will need to work on that because clearly every team is going to pursue that tactic against him.
Adil Rashid reached 50 T20 international wickets and went for an average of just 5.83 runs per over in the series; he is genuinely world class and he has been for a while.
He is armed with a googly which batsmen still cannot pick. He bowls it brilliantly and disguises it beautifully.
I was a bit surprised England did not give some others players a go for the last T20, having already secured the series.
With everything that is going on, it is quite a commitment for players to fly out, quarantine for two weeks and then do all the training, only to then sit and watch on.
But England do not play many T20s, so to be fair to Morgan he is trying to squeeze in every opportunity to find the team he likes.
'Sensible to rest Stokes, Archer and Curran for ODIs'
With almost three years to go until England defend the 50-over World Cup, now is the time to put in the groundwork and start building a team for that tournament.
On Friday in Cape Town, they play the first of a three-match ODI series against a pretty weak South Africa side, weakened more with the loss of Kagiso Rabada due to injury.
It is a real shame because Rabada is a standout bowler. You always want the opposition to be at full strength.
Jofra Archer, Sam Curran and Ben Stokes have been rested and I think it is a sensible decision to send them home.
Those three have all been in bio-secure bubbles for a long time, dating back to the summer, you cannot really live your life like that.
Yes, the trio did decide to play in the Indian Premier League and some people may feel that England should come first, but I think you have to realistic and remember it is a case of give and take.
They now need some oxygen, get some fresh air and have a bit of family life.
Stone and Wood to get their chance & Root's return
This one-day side is the hardest England limited-overs team to break into in memory. Liam Plunkett was moved on after the World Cup win but there are no other real gaps in the side.
So therefore resting Curran, Archer and Stokes gives you an opportunity to see other players - you cannot just play your best team in every single game.
It is nice to see Olly Stone being selected and hopefully Mark Wood gets a game because his pace is important. With Lewis Gregory, we saw in New Zealand last year what a great all-round cricketer he is.
Then we have Joe Root returning to the team having not been a part of the T20 squad.
The Test captain takes a backseat when the one-dayers are on and it works OK, there is no issue with the split captaincy at all.
Root has huge admiration for Morgan and it helps that Morgan clearly has no desire of being a Test captain.
Sometimes there can be issues when the one-day captain is often the younger, fitter, sleeker model who has his eyes on the Test captaincy but that's not the case here.
Root is a terrific, busy, inventive, innovative one-day batsman and it will give him a chance to play some cricket, which he hasn't done in a little while.
Jonathan Agnew was speaking to BBC Sport's Kal Sajad.