England all-rounder Ben Stokes could find himself in trouble after appearing to swear at a fan as he walked off the field on the first day of the final Test against South Africa in Johannesburg.
England leads 2-1 and can clinch the series with a draw at the Wanderers, which is renowned in South Africa for its raucous crowds.
A record 10th-wicket partnership saw England amass a formidable first-innings total before rampaging through the home's team batting order to take a stranglehold on the game and move closer to a series victory.
South Africa now have a maximum of 196 overs to attempt what will be a record chase, should they manage to get to 466 over the next two days.
Chris Woakes was the bowler, drawing a leading edge from Vernon Philander who was at the start of a deeply disappointing day.
It was only Quinton de Kock - as he has done all series - that offered any resistance with his fourth half century of the series.
Vernon Philander has suffered a grade two hamstring tear in his final Test appearance, which limited him to nine balls in England's second innings, though South Africa's head coach Mark Boucher confirmed he will be available to bat.
It took Ben Stokes to break things up, Pretorius feeding a rising delivery to Zak Crawley at gully, before Wood wrapped things up.
De Kock did not last long soon after, with Mark Wood going past his defences to remove him for a well-played 76.
Root had the lunch break to ponder his options but was never likely to put the burden straight back on his bowling unit and instead asked Crawley and Dom Sibley to strap on the pads.
"In addition to this incident, members of our support staff were subjected to personal abuse during and after the day's play".
Sibley matched his first-innings score of 44 before exiting in familiar circumstances after tea, shuffling across to left-armer Beuran Hendricks and nudging to short midwicket.
Speedster Anrich Nortje (2-61) blasted out Ollie Pope (11) and the out-of-form Buttler (8) - both caught behind, with the first earning De Kock his 200th Test dismissal.
Wood led the way in the evening session with 3-21 as England removed Pieter Malan (15), Rassie van der Dussen (0), Dean Elgar (26), Faf du Plessis (3) and Temba Bavuma (6) with their five-man seam attack generating real pace off the quick wicket.
Root seemed largely immune to the frenzy but Sam Curran joined in, sprinting to 35 before hooking Hendricks to fine-leg.