Steven Finn led a persistent England bowling attack as South Africa failed to capitalise on a promising start on the first day of the third Test at the Wanderers Stadium on Thursday.
South Africa were 267 for seven at the close, a disappointing return after reaching 117 for one at the mid- afternoon drinks break.
Having negotiated what could reasonably have been expected to be the trickiest part of the day - after winning the toss and batting in cloudy conditions on a pitch with pace and bounce — wickets fell at regular intervals.
South Africa slipped to 225 for seven before Chris Morris and Kagiso Rabada took them to the close with an unbeaten partnership of 42.
Elgar's dismissal, pushing at an off-spinner from Moeen Ali to be caught behind by Jonny Bairstow, started a slide. It ended a second wicket partnership of 73 with Hashim Amla, who fell to a superb delivery from Finn shortly afterwards for 40.
The tall Finn was hostile throughout the day, taking the wickets of Amla and Faf du Plessis for a return of two for 50. Ben Stokes took two for 46, including the key wicket of new captain AB de Villiers, who looked in supreme form.
Brief Scores
SA: 267/7 (Morris 26*, Rabada 20*) vs England.