Ellyse Perry's Australian Test record of 213 not out has helped her team to put one hand on the Ashes, but England are threatening late resistance in the women's day-night Test in Sydney.
After Perry brought up the world's third-highest Test score, Australia declared at 9-448 on Saturday with a 168-run first-innings lead.
England faced a difficult 17 overs under lights at North Sydney Oval, but openers Tammy Beaumont (25no) and Lauren Winfield (12no) survived to get to stumps at 0-40 on the second-last night of the four-day Test.
Perry's double century capped off a record-breaking evening for the Aussie women, who finished with their third-highest total and the best effort of any team on Australian soil.
See the moment Perry reached her century:
It also put them in a commanding position to retain the Ashes, with a win enough to to claim the series under the multi-format points system.
Even if England can manage a draw, they will need to win each of the three Twenty20s to wrest the urn back.
Perry wasn't alone on the third day, putting on 102 runs for the sixth wicket with Alyssa Healy (45). Debutante Tahlia McGrath (47) joined her for an Australian record seventh-wicket stand of 103.
Allrounder Jess Jonnasen provided a late cameo as she hit 24 from 39 balls before she holed out trying to attack Laura Marsh (3-98).
Amanda-Jade Wellington was trapped lbw by Ecclestone (3-107) for two, before No.11 Megan Schutt played out a crucial six deliveries to see Perry to her double century.
Perry was patient on Friday early in her innings, but upped the tempo on Saturday as she hit 11 boundaries in her second 50 to bring up a century just under four hours with 26 boundaries and one six.
Her innings eclipses Karen Rolton's 209 not out against England in the 2001 Ashes and, internationally, is the third highest behind Pakistani Kiran Baluch's 242 in 2004 and Indian Mithali Raj's 214 in 2002.
She ended up with 26 boundaries, and one six back over Ecclestone's head to finish the innings.
It marked the first time the dual international had reached three figures in any form of the game for Australia after passing 50 on 28 occasions.