Just as summer inexorably turns into autumn, so England's grip on the No.1 Test status is ebbing away as surely as night follows day. Like a desperate man losing their grip on a cliff face, England will, at some stage on Monday, fall from their perch. As Bob Dylan put it, it's not dark yet, but it's getting there.
Few England supporters would dispute that South Africa have been the better side in this series. They would accept, too, that England, for all their improvements over recent years, have failed to justify their lofty ranking since defeating India about 12 months ago. What seemed, at the time, like the start of a journey, might have turned out to be the end. A record that may well read six losses from 11 Tests this year by the end of Monday tells its own story.
It is a story which leaves England with some awkward questions to answer.
Firstly, they need to look at why their catching, so impressive when they won the Ashes, has become so fallible. They have dropped nine catches in this series, including chances that might - such as the reprieve of Hashim Amla at The Oval and Alviro Petersen in Leeds - have defined matches. In South Africa's second innings here, England dropped Amla on 2, AB de Villiers on 8 and Jacques Rudolph on 6. It is hard enough to beat South Africa without allowing their middle order an extra innings each.
At present this is a question for which England have no answer. They are not lacking in hard work and good intention but, perhaps, lack the personnel to build an effective slip cordon. It may be that, if they conclude that their slip catching is costing them games - and there is increasing evidence that it is - they need to look at their team selection and ensure they are better covered in such respect.
Stuart Broad's reputation has also declined during this series. Despite one good spell at Leeds, he has been bowling with reduced pace and effectiveness throughout and can no longer be presumed an automatic selection. While the greater potential of his batting might be presumed to see him preferred to Graham Onions, Broad's batting average in this series - 8.25 - hardly justifies that. The bowling average of 39.72 is hardly encouraging, either.
That is not to say Broad should be dropped. He is only 26 and may well come to be regarded in time as one of England's finest seamers. But England really do need to question - and correct - his loss of pace and hostility with the ball and his loss of form with the bat. He is too good to be allowed to go to waste.
But perhaps the most awkward question concerns Andrew Strauss. No-one disputes that Strauss is a fine man with an excellent career behind him. But there are legitimate questions about his future. He has a highest score of 37 and an average of just 17.83 in this series. More to the point, he has hardly looked likely to score runs.
Some of his tactical decisions - such as dropping Graeme Swann at Headingley and the leg-side approach to bowling at Graeme Smith - have been muddled and, by the close of play on Monday, it is likely that he will have presided over one series victory in four. The harsh might also suggest that a more sophisticated captain might have nullified any issues between Kevin Pietersen and the rest of the team before they reached the stage they have. They have been brewing for some time.
It is true that it is not long since Strauss scored runs against West Indies. And they were not the easy runs some suggest. As Kemar Roach proved to Jonny Bairstow, the West Indian attack is not to be under-rated. But the fact remains that the South African attack is a class above and, if England really aspire to return to the top ranking, they need a man at the top of the order who can see off the new ball with more certainty that Strauss offers at present. The lack of alternatives for his position is a concern, but Jonathan Trott, Nick Compton, Michael Carberry and, perhaps, Joe Root are all possibilities.
England's success has been built - partly, anyway - on the principle of continuity of selection. But there is a line between a settled environment and a cosy environment and it remains to be seen if Andy Flower, for all his excellence in the role of England coach, can regenerate this side in the way that Sir Alex Ferguson has a series of Manchester United sides.
Perhaps this series may prove something of a watershed. The emergence of Steven Finn and Jonny Bairstow offers substantial encouragement for the future. Both are young and both will endure some pot-holes on their journey, but they have shown they are men with a future at this level.
Finn has claimed eight wickets in this match, bowling with a pace and hostility that would trouble any side. He concedes more runs per over than England would like in an ideal world, but the key is that he takes wickets. It is a skill that outweighs all negatives. He has time to work on his consistency.
"I wouldn't say I chase wickets," Finn said after play. "I'm a young bowler. I'm not going to get it right every time. That's part of being a young bowler. Everyone experiences that when they're growing up. I'm only 23-years-old. I'm still learning a lot about the way I bowl. I don't run up thinking 'wickets, wickets, wickets' every ball. It's not the way I've been taught to operate and it's not the way the team operates. I went at four-an-over in the first innings, but came back in the second innings and went for less than three-an-over and felt I bowled well."
Finn insisted that England could still win the game on the last day. But to score another 330 in 90 overs against this attack would be an awesome achievement. But perhaps the most damning statistic is this: England have never successfully chased more than 332 to win a Test in a history that started in 1876-77.
"As a team over recent years we have enjoyed breaking records and defying people's beliefs against us," Finn said somewhat implausibly. "We really do believe in the dressing room that we can win this game. The older ball does a lot less than the new ball and tomorrow we'll be playing against a ball 15 overs old. When the ball is softer there is no uneven bounce and when the ball is old and the sun is out, it's a very good wicket to bat on. It's going to be important to build partnerships and get our foot in the door. Then, later in the day, maybe we can smash through it and win the game."
Maybe. In truth England need a miracle of Biblical proportions to win this game and retain their No.1 ranking. And it is hard to see how even a plague of locusts can help them now.