Explainer: Why Starc catch of Duckett was ruled not out

Australia thought they had claimed the key wicket of Ben Duckett in the day's dying embers, after the England left-hander top-edged a Cameron Green delivery to deep fine-leg.

The ball was grasped by Mitchell Starc running and sliding to his left, though replays showed the ball was scraped across the turf by the Australian fielder in the moments afterward.

Law 33.3 of the MCC's Laws of Cricket states that "the act of making a catch shall start from the time when the ball first comes into contact with a fielder’s person and shall end when a fielder obtains complete control over both the ball and his/her own movement."

In this case, it was deemed by third umpire Marais Erasmus upon review of the catch that Starc was not in control of his own movement when the ball was brushed against the turf.

The MCC re-affirmed this interpretation on Twitter.

"Law 33.3 clearly states that a catch is only completed when the fielder has 'complete control over the ball and his/her movement'.

"The ball cannot touch the ground before then. In this particular incident, Mitchell Starc, was still sliding as the ball rubbed the ground, therefore he was not in control of his movement."

The law in question has seen several instances of its application in recent Test matches, both across the first two Ashes encounter and the ICC World Test Championship Final last month.

Steve Smith held a catch to remove Joe Root in the first innings at Lord's, deemed fair by Erasmus after review, while at Edgbaston a catch by Marnus Labuschagne was adjudged not out in a similar application of the law to Starc's.

Cameron Green's grab to remove Shubman Gill in the WTC23 Final also came under the microscope of the third umpire Richard Kettleborough, though the all-rounder was deemed in control off the catch with fingers underneath the ball as hand and ball hit the turf.

After the ruling late on day four at Lord's, Duckett (50*) went on to survive the evening alongside skipper Ben Stokes (29*), though England sit precariously on 114/4 and need a further 257 runs to draw level in the five-match series between the arch-rivals.

Cummins, Starc help Australia take control of Test