Mooney's first half century in T20 internationals became the highest score in this format by an Aussie in Australia, and was rounded off by hitting the winning runs through cover in front of 3932 delighted fans with 4.1 overs to spare and six wickets still in the shed.

That gave Mooney's team an unassailable lead in the series with two T20s in Canberra still to play, and marks the ninth time Australia has beaten England in an Ashes series.

"You think back to earlier this year it was just utter disappointment when we lost that semi-final in the World Cup, I'm just really proud of the team, they've just done a great job," Australian captain Rachael Haynes said.

"It's a great feeling, one of a little bit of relief but one of real excitement as well.

"In a run chase you never want to leave it to the last moment. The way Beth came out with that intent, it was awesome to watch. The way she took control of that was fantastic."

The T20 win came five days after the visitors dug in to stave off a Test defeat at the same venue.

Megan Schutt was unstoppable again with the white ball, taking 4-22 and she now has 16 wickets for the series.

Test double centurion Ellyse Perry contributed again taking two wickets herself, but her batting for once failed to fire. She faced only two balls on this occasion, having soaked up 374 without fail in the Test, before tamely offering a leading edge back to Danielle Hazell.

But it was all trivial. This was the Mooney show from the outset, and she batted beautifully to finish off this series after she was overlooked for the three one-day internationals that begun the Ashes.

"I just had the mindset of hitting the ball if it was in my zone and just getting off strike if it wasn't," Mooney said.

"It's really hard in T20 cricket, you're never sure you're going to win until you actually do it. Chases like that, just above a run a ball - small totals in T20 cricket, they're really tricky ones and you lose a couple of wickets early and you're chasing your tail a bit.

"I was just really happy to get given an opportunity and really happy to take it. That's the nature of the beast of elite cricket, someone has to miss out and unfortunately that was me [in the one-dayers]."

Mooney was the second-highest run scorer in last season's Women's Big Bash League for the Brisbane Heat, and the mantle is hers for the taking this time around with Australian captain Meg Lanning out for the summer with a shoulder injury.

This match was a treat for the Sydney fans who endured lengthy patches of dullness in the drawn test, although England were forced to do it without World Cup hero Anya Shrubsole, who was ruled out with a hamstring injury.

It began in the most bizarre fashion after Australia won the toss and bowled, with England captain Heather Knight dismissed second ball, adjudged bowled by Jess Jonassen.

Knight was called back after it appeared wicketkeeper Alyssa Healy had broken the stumps with her gloves before she was sent packing a second time when it was decided the luckless opener had in fact edged it.

A bizarre England innings followed in which Australia dropped five catches as the visitors racked up 9-132.

Australia had four wickets within five overs and their tails up, before Danielle Wyatt fought back with a superb half century in her first game of this Ashes series.

Wyatt batted fearlessly in her first T20 international since July last year, taking on the firing Australian attack with an array of strokeplay and blasting six boundaries.

She too was dismissed in unusual fashion a ball after bringing up her first 50 in 124 internationals. Wyatt punched one back and it was fielded superbly by Ashleigh Gardner, who slung it into Healy affecting a run out.

"The girls are really hurting at the moment but we really want to turn it around quickly and finish this tour with a bit of a high," Knight said.

"T20's a game that can change very quickly. Losing those four wickets, you're really chasing the game and obviously that cost us.

"Australia's a tough place to play cricket. I couldn't be more proud of how the girls have fought and stood up to that toughness and tried to throw a few punches back."