Australia captain Pat Cummins starred with the ball and Alex Carey made valuable runs following a dramatic collapse as the holders retained the advantage in the World Test Championship final against South Africa on Thursday.

Fast bowler Cummins produced a sensational spell of four wickets for one run when South Africa were dismissed for 138 on the second day in reply to Australia's first-innings total of 212 at Lord's.

Australia collapsed to 73-7 in their second innings, with Kagiso Rabada (3-44) and Lungi Ngidi (3-35) doing the bulk of the damage.

But Carey (43) and Mitchell Starc (16 not out) shared an eighth-wicket partnership of 61 before the wicketkeeper was lbw to Rabada shortly before the close.

The last over of the day saw Starc dropped on 14 when Marco Jansen shelled a routine catch off Wiaan Mulder.

At stumps Australia were 144-8, a potentially decisive lead of 218 runs.

A remarkable 28 wickets fell in two days on a pitch which, while offering some assistance to the quicks, was by no means unplayable. Nevertheless, a match scheduled for five days, could now finish before the end of the third.

Rabada, who had taken 5-51 in the first innings, tormented Australia again with two wickets in the 11th over. He had Usman Khawaja caught behind for six and, two balls later, removed Cameron Green for a duck.

Green's exit meant the number three had faced just five balls in the match for a total of four runs. Wickets continued to tumble after tea.

Left-arm quick Jansen had Marnus Labuschagne, in his first Test as an opener, caught behind for 22. And Australia's 44-3 became transformed 48-4 next over when Beau Webster, who top-scored in Australia's first innings with 72, fell lbw to Ngidi.

Australia were reeling at 73-7 after Cummins was bowled off his pad by an excellent Ngidi yorker. But Carey and Starc led a defiant response that kept their side on course to retain the title.

Earlier, Cummins finished with figures of 6-28 as he reached 300 career Test wickets and secured a coveted place on the Lord's honours board with a five-wicket haul.

South Africa lost their last five wickets for 12 runs as Cummins ripped through the order.

Only South Africa captain Temba Bavuma (36) and David Bedingham (45) offered meaningful resistance during a fifth-wicket stand of 64.

After lunch, Cummins struck four times in a mere 17 balls of devastating pace bowling.

South Africa had resumed on Thursday at 43-4, battling to put enough runs on the board.

Bavuma, who faced 37 balls for his overnight three not out, changed gears with a lofted cover-drive fo four off left-arm quick Starc for four before he pulled Cummins for six.

Cummins had his revenge, however, when Bavuma's checked drive was brilliantly caught at cover by a diving Labuschagne.

He then dismissed Kyle Verreynne lbw for 13 and, three balls later, held a simple return catch as Jansen fell for a duck. 

The Australia skipper ended the innings with his 300th Test wicket, Rabada well caught low down at deep square leg by Beau Webster. Cummins received a standing ovation as he led his side off the field.

That reception was a marked contrast to the boos that echoed round Lord's two years ago after Cummins refused to withdraw an appeal following Carey's controversial stumping of Jonny Bairstow during an Ashes Test.