England v Australia: Biggest game of our careers - Stuart Lancaster

England face the "biggest game of their careers" against Australia as they fight to keep their World Cup dream alive, says coach Stuart Lancaster.

About 82,000 will be at Twickenham on Saturday, and defeat means England would be the first World Cup hosts to fail to reach the knockout stages.

They have won four of the past five meetings with Australia.

"It is a huge game, at home. With the whole country behind us, we'll be difficult to beat," Lancaster said.

Australia have won both their matches in the tournament, while England let slip a 10-point lead with 30 minutes remaining to lose 28-25 to Wales in their previous encounter.

Almost 12 million people watched the closing minutes of that game, a 49% share of everyone watching television at the time, and a similar audience is expected on Saturday.

England and Australia have met five teams previously in the World Cup, with the Wallabies winning the first two and the Red Rose triumphant in the last three, including the 2003 final in Sydney.

Lancaster admitted that losing against the Wallabies "has preyed on my mind".

"We're obviously aware what's at stake, you don't have to be a rocket scientist to work it out," said Lancaster.

"I understand the consequences. I understand the accountability and responsibility for delivering in this World Cup, 100%."

Wallabies head coach Michael Cheika says his players will be "letting the country down" if they do not perform with the level of intensity he expects.

"Every moment in the jersey should be cherished," he said. "Every game should be like your last."

England know - following Wales' 23-13 victory against Fiji - they will be eliminated by an Australia win.

But if Lancaster's side win they will move above the Wallabies into the second qualifying spot. And with Uruguay - the lowest-ranked team in Pool A - to come in their final match on 10 October, they would be in a strong position to reach the quarter-finals.

If England and Wales are tied in second place after their final matches, Warren Gatland's men would go through thanks to their head-to-head record.

However, if England, Wales and Australia all finish on the same number of points, the top two will be decided by points difference.

The pool is a particularly tough one - at the start of the tournament it contained four of the world's top nine as the draw was made in December 2012 when England had slipped out of the top tier of seeds and Wales were in the third tier of seeds.

The hosts have made three changes from the Wales defeat, with fit-again centre Jonathan Joseph recalled in place of Sam Burgess and number eight Ben Morgan and lock Joe Launchbury replacing the injured Billy Vunipola and Courtney Lawes.