A record partnership worth 301 runs appears to have taken the game away from England, and with it, possibly the Ashes series.
Smith and Marsh put on record stand to hand Australia control of Ashes Test in Perth
An unbeaten 301-run stand by captain Steve Smith and Mitchell Marsh struck a heavy blow against England's hopes of keeping the Ashes out of Australian hands on Day 3 of the third Test at the Waca on Saturday.
On an agonising day for Joe Root's team, Smith broke the bowlers hearts with his second double-century after all-rounder Marsh celebrated his maiden ton.
The pair pushed Australia to 549-4 and a first innings lead of 146 runs, rendering England's 403 hopelessly inadequate.
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They strode off to a standing ovation, with Smith unbeaten on 229 and Marsh 181 not out, pushing toward a double-century of his own.
"It felt really good yesterday, I was in the zone. I wanted to cash in today," Smith said before he exited the ground. "We wanted to be out in the middle and just keep batting."
On Day 2, Dawid Malan and Jonny Bairstow had England full of optimism after building a 237-run stand for a record fifth-wicket stand in Tests at the Waca.
The mark lasted less than a day, as Smith and Marsh smashed 57 boundaries between them to leave England hoping for rain.
Showers are forecast for Days 4 and 5, but the weather may not be enough to save England, who managed only a single wicket despite no fewer than seven players rolling over their arm throughout the day.
Having torched England for 107 runs in the middle session, Smith and Marsh plundered another 128 after tea, as England's bowlers battled fatigue and the inescapable knowledge that none of their plans were working.
Having punished England with 215 at Lord's in 2015, Smith set himself a new personal best in a masterclass of patience, precision and timing.
His unbeaten 390-ball knock has him fourth on the list of highest innings at the Waca, with the possibility of further promotion on Day 4.
He reached the three-figure mark, his seventh against England, when he whipped paceman Stuart Broad through the leg side for four.
The second hundred with a single off all-rounder Moeen Ali, and he bounded down the wicket roaring in triumph to the delight of a sell-out crowd.
Marsh celebrated his recall with his maiden Test century, completing a rare family trio of Ashes tons.
His brother Shaun Marsh scored an unbeaten 126 in the second Test win at the Adelaide Oval, and his father Geoff, beaming with pride in the heaving crowd, posted 138 as an opener at Nottingham in the 1989 series.
Marsh cut paceman Stuart Broad to the fence to bring up his ton from 130 balls, and hammered the English attack with a barrage of straight drives.
Moeen removed Shaun Marsh for 28 in the first hour of the day. It was to prove England's only highlight through a demoralising day.