Dropped catches have dogged South Africa throughout this series and yesterday they downed five - two very hard, two difficult and one (Moeen) inexplicable. The venue had been inundated by an overnight deluge making outfield conditions soggy.
The hosts finished the day on 224-8 with a lead of 360 with two days remaining in the Test series.
With his two partners in crime unable to assist him ably - and Kyle Abbott opting to play for Hampshire rather than pursue his worldwide career - Morne Morkel has been the shining light for South Africa.
Dean Elgar, a player who has embodied much of their spirit, duffed a relatively simple chance from Moeen Ali at slip on 15 and with it the series was perhaps finally gone. So it was that when Amla finally went, out lbw on review to Moeen for 83 after more than three hours at the crease, England struck twice more.
Assistant coach Paul Farbrace reiterated that position at the close of play, adding: "We've obviously heard the news tonight, but I promise you we've had nothing official".
Ali played two pivotal parts in the series-clinching victory, first hitting a flamboyant 75 not out in England's second innings to ensure the lead was out of South Africa's reach.
After establishing a healthy first-innings lead of 136, England lost three wickets either side of lunch.
Stuart Broad had No 11 Duanne Olivier caught off a top- edged hook by Jonny Bairstow, who on Saturday had made a valuable 99 and claimed his 100th dismissal as a Test wicket- keeper. Kagiso Rabada took four wickets.
England's Man of the Series Moeen Ali and captain Joe Root joined Michael Atherton at the presentation following their 3-1 series victory over South Africa.
In its first series under Root, England was ultimately convincing in three of the four tests, with its only wobble coming in a heavy defeat in the second match at Trent Bridge.
Dawid Malan was also dropped - a tough chance to Temba Bavuma as he ran back from point - but soon prodded the ball via bat and pad into short leg's hands off spinner Keshav Maharaj.
Despite taking 10 wickets in the series-opening win at Lord's Ali was insistent that he was not England's frontline spinner, and he says that helped him.
Root (49) and Ben Stokes (23) then shared a stand of 57 before they both fell to Olivier, only playing this match after back injuries ruled out both Vernon Philander and Chris Morris.