Cricinfo reported Law 2.12 on any reversal of an umpiring decision as: “An umpire may alter any decision provided that such alteration is made promptly. This apart, an umpire's decision, once made, is final.”
The law does not specify what “prompt” means in real time.
Reversal of fortune
In a savage twist later in the day, second slip Aiden Markram claimed a catch that also invited intense scrutiny. India's stand-in captain KL Rahul was given the finger and that decision stood in the absence of evidence that clearly showed the umpires erred.
Rahul shook his head as he departed the scene, perhaps partly too as a result of the clear directions he likely received to the showers from the helpful South African fielders.
Earlier, Van der Dussen's demise was in tune with eventful passages in this Test with the whiff of lunch in the air.
India lost their two most experienced batsmen before the break on the first day and on Tuesday in the half-hour before lunch Elgar, Keegan Petersen and Van der Dussen faced the dreaded long walk up the steps.
While at the crease, Petersen looked a delight as he seamlessly engaged lower and higher gears as the occasion demanded in his 118-ball innings.
He recorded a maiden Test 50, on the back of the diligence that comes from playing with a straight bat, and it was only after he reached that milestone that he allowed himself to luxuriate in the occasion.