England were 357 for five at stumps, having collapsed to 76 for four before lunch on the first day of the opening Test of a four-match series.

But Root´s 12th hundred in 54 Tests, and third at Lord´s, justified his decision to bat first after winning the toss in what was England´s first match at this level since he was appointed following Alastair Cook´s resignation as skipper in February.

New vice-captain Ben Stokes made 56 and helped wrest the initiative away from the Proteas in a fifth-wicket stand of 114.

Moeen Ali´s 61 not out cemented the recovery as he added an unbroken 167 with Root.

Concerns had been expressed that captaincy would reduce Root´s effectiveness as a batsman.