People often talk in sport about something being "a watershed moment" - a turning point or a fundamental change in direction or attitude. England's win was just such a moment. It was all the better because it was never really expected, and England won despite not really playing their best cricket.
When new coach Mark Robinson decided it was time to move on from the Lottie Era it was a tremendous statement of trust in the girls who remained in the squad that they could do the job for England, without their former captain and leading run scorer.
Frequently in interviews Robinson would state that the girls really never knew how good they were. What they lacked was confidence in their own abilities. On Sunday they began to show that Robinson's confidence in them was not misplaced and that their confidence in themselves, and as a team, is on the way up.
It was not a faultless performance by any means. Anya Shrubsole and Nat Sciver dropped catches they would normally take in their sleep, and the batsmen will be annoyed that they made good starts, got the pace of the wicket, but did not go on. But whereas such lapses would have led to a collective dropping of heads, this time there was a determination to do better next time. Each batsman who came to the crease knew they could do a job - this time it was left to Katherine Brunt and Jenny Gunn to be the ones to take the England innings from ordinary to enough to give the Aussies something to think about.
In the field Heather Knight's ground fielding was exceptional as she led her team from the front and Nat Sciver held her nerve as she caught Ellyse Perry on the boundary edge at cow corner in the dying embers of the game.
Mark Robinson won't be getting too excited just yet, and there will no doubt be some dark days amongst the good ones, but inside he will be relishing the next few days with the hope of some more signs that this England team have got what it takes.
Here is who plays who in the next five days, with the top four qualifying for the semi-finals :-
England - New Zealand & West Indies
Australia - India & South Africa
India - Australia & New Zealand
New Zealand - England & India
South Africa - Sri Lanka & Australia
And here is how they stand to date...