If England persevere with Jennings, he might fill his boots in the three-Test series against the weak West Indies attack, keep his place and then be traumatised by the Aussie quicks.
Root began his reign by conquering South Africa.
Dropped catches have dogged South Africa throughout this series and yesterday they downed five - two very hard, two difficult and one (Moeen) inexplicable.
Broad had earlier claimed the final wicket of South Africa's first innings.
South Africa added just six runs to their overnight total before Duanne Olivier top-edged a pull off Stuart Broad to wicketkeeper Jonny Bairstow as the Proteas were dismissed for 226.
England set South Africa 380 to win, and bowled the tourists out for 202 in their second innings soon after tea.
But figures of 4/38 in 17 overs gave Anderson, who had struck four times from the newly named James Anderson End on Saturday, his best innings return at Old Trafford. "He has come on leaps and bounds as a cricketer and this series has really defined him as a player for us".
The pair looked to have dug themselves in but spinner Moeen Ali, a hat-trick hero in the third Test, tempted Kuhn forward with a nicely flighted delivery and Ben Stokes pocketed the catch at slip. Thirty-four balls later South Africa were all out and their long race was run‚ and lost.
England remain strong favourites to win the fourth Investec Test after Moeen Ali's late strokeplay arrested their second-innings slide. Before Ali's entrance, England was in some trouble at 129-5 and then 153-7. "But I just want that last wicket, I don't care who gets it", said the 35-year-old.
"I'm just going to do exactly what I've been doing and try to spin it as much as I can".
With that, the Proteas were all but done.
South Africa's AB De Villiers and Faf Du Plessis (right) during ICC Champions Trophy nets in June.
Although the comfort of their first-innings lead meant there would have been few nerves in the England dressing room, the hosts were struggling at 134-6 when Moeen walked to the crease.
Earlier, England resumed on 260 for six after winning the toss.
Media reports say that South Africa do not intend to retain their current coach Russell Domingo after the conclusion of the series with England.
"It's a real luxury to have", Root said.
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