Although each test stands on its own, once a team has won a series , despite all the efforts to be up for a dead rubber, subconsciously there isn't the same intensity to win. South Africa aren't a bad side and their demise has been over exaggerated. I think Amla is the best batter in the world and Morkel is a fine bowler. Add to those two, AB De Villiers and the new boy Rabada , plus De Kock and not forgetting Steyn ( best bowler in the world) and Philander. Also their Cook has looked the best opening batsman on both sides. With players of that calibre I don't think they'll drop too far in the rankings
Taking into account everything, it's been a great series win, on a par with the win in India a couple of years ago.
I agree with Mattyblue, our top order batting needs looking at, too many collapses. We had a similar problem when we won the Ashes last summer but having said that, if we're beating Australia at home and South Africa away , things aren't too bad with the state of English cricket
Now onto the ODIs and T20s , where we've been showing good improvement recently.