Nathan Lyon was hailed as Australia’s “key” bowler as the team closes in on an emphatic victory in the final Ashes Test after beleaguered England unravelled on a torrid day in Sydney on Sunday.

The Australians amassed a massive 303-run innings lead in blistering heat and then reduced the battle-weary tourists to 93 for four at the close with a day to play.

Compounding England’s woes was a finger injury for skipper Joe Root, his team’s last major hope of staving off a 4-0 series rout on Monday’s final day of the Test.

Root was unbeaten on 42 at the close with Jonny Bairstow not out 17.

Lyon captured the important wickets of Alastair Cook and Dawid Malan to have two for 31 off 19 overs at stumps.

“I think Gaz (Lyon) is the key tomorrow. The wicket is definitely suiting his conditions, especially with the left handers, he’ll come into play,” Australian centurion Shaun Marsh said.

“I thought he bowled really well today and showed his class and hopefully he can come out tomorrow and get a few early breakthroughs for us.”

Australia called a halt to their epic first innings at 649 for seven, and soon had England in trouble after the tourists had been cooked in the field for more than two draining days.

Mark Stoneman was leg before wicket to Mitchell Starc for a duck and lost a review in the process, and next ball Cook was put down at first slip by Marsh off Josh Hazlewood for five.

But Cook’s reprieve did not last long and he was bowled for 10 when a sharp Lyon turner hit the top of off-stump in the off-spinner’s first over.

Cook, who became during his innings only the sixth batsman to score 12,000 Test runs, finished the series with 376 runs at 47.

James Vince survived a caught behind off Lyon on review on 15, but three runs later edged Pat Cummins to Steve Smith at slip.

Dawid Malan followed when Lyon trapped him leg before wicket for five.

Ton-up brothers

Shaun and Mitchell’s overflowing emotions on scoring centuries batting together almost ended in disaster.

The Marsh boys became only the third set of brothers to score centuries in the same innings for Australia.

They joined Greg and Ian Chappell and Steve and Mark Waugh to score fraternal centuries for Australia, but it could have ended very differently.

Mitchell Marsh embraced his elder brother mid-pitch before sensing danger and scrambling back to his crease to avoid being run out.

“That was my fault,” admitted Shaun. “I think emotions sort of got the better of me and I just wanted to give him a hug.

“I saw him starting to celebrate and I lost all concept of where the ball was and what was happening with the ball.

“He pushed me off him and said ‘you better get down the other end.’

“Thankfully, it all worked out and I was just really happy for him.”

Mitchell added: “My take was I pretty much went for the high five and Shaun went for the hug and we were somewhere parked in the middle and had a quick split-second level of panic and hugged again after that.”

Shaun was left on 98 overnight, but cracked a cover boundary off the day’s opening over to bring up his sixth Test century.

“To be out there to watch Shaun hit that cover drive and embrace in the middle for his hundred and then have him out there for mine is something that we’ll look back on in a few years and really cherish,” Mitchell said.

Shaun, whose selection for the series was criticised, has more than justified his place in the Australian side with 445 runs at 74.16, while all-rounder Mitchell, who came in for the third Test, has scored 320 runs at 106.66.

Shaun said it was a proud moment for the family, with his father, Geoff playing 50 Tests as opener from 1985-1992.

“To be out there with Mitch, to both score our Test century today for Australia, being out there and sharing each other’s emotions when we got to our hundreds, was an extremely happy moment,” he said.

“And it’ll certainly be a day that we won’t forget.”