In pictures: England poised for victory in third Test against South Africa after Joe Root takes four wickets

Captain takes career-best figures as Proteas head for humiliating defeat in Port Elizabeth

England fielder Ollie Pope dives to catch out South Africa batsman Rassie van der Dussen during Day 4 of the third Test in Port Elizabeth on Sunday. AP

Ollie Pope catches out Rassie van der Dussen off the bowling of Joe Root. Getty

Joe Root celebrates after taking the wicket of Rassie van der Dussen. Getty

South Africa captain Faf du Plessis goes on the attack. Getty

Quinton de Kock after losing his wicket. Getty

Mark Wood of England takes a catch to dismiss Quinton de Kock. Getty

England bowler Sam Curran. Getty

South Africa batsman Dean Elgar is bowled by England's Mark Wood. AP

England's Sam Curran. AP

Faf du Plessis of South Africa. AP

Stuart Broad of England celebrates after bowling Keshav Maharaj. Getty

England captain Joe Root leads his team onto the field at the start of Day 4. Getty

England spinner Dom Bess celebrates his five-wicket haul at the end of South Africa's first innings. Getty

South Africa's Dean Elgar. AFP

Sam Curran of England celebrates after bowling Quinton de Kock. Getty

South Africa's Keshav Maharaj is bowled by Stuart Broad. AFP

Mark Wood of England keeps himself entertained before the start of Day 4. Getty

Spouth Africa were put to the sword by an unlikely foe in the third Test on Sunday after being forced to follow on by England.

The gentle spin of captain Joe Root proved unusually deadly as he took 4-31 in Port Elizabeth – his best figures in Test cricket – to leave South Africa on 102-6, still 188 runs short of avoiding an innings defeat.

Barring one extremely long intervention by the weather, the tourists look assured of taking an unbeatable 2-1 series lead into the final Test starting in Johannesburg starting on Friday.

They needed only 28 balls to dismiss South Africa's last four batsmen for the addition of a single run at the start of play, with Stuart Broad picking up three of the wickets without conceding a run.

Rain early in South Africa's second innings threatened to thwart England's push for victory but fast bowler Mark Wood struck twice when play resumed more than three hours later.

Wood used his extreme pace to send Dean Elgar's off stump flying out of the ground before he had Zubayr Hamza feeling for a ball outside his leg stump to present a catch to wicketkeeper Jos Buttler.

"I love it," Wood said of his return to Test cricket after almost a year out of the side and his first match of any type since being injured in the World Cup final last July.

"I'm wrapped up like a mummy in my left leg," he said of the strapping aimed at preventing further injuries. "Bowling Elgar was a great feeling."

Root took the next four wickets, bowling from the same end from where fellow off-spinner Dom Bess took five wickets in the first innings.

Wood said: "He does get key wickets when he bowls and he's been working at it in the nets. At practice he's been doing a lot more bowling."