England's preparations for their World Cup quarter-final against Australia have been given a significant boost with the news that Billy Vunipola is now "very likely" to be fit to start.

The number eight injured his ankle against Argentina 10 days ago but continues to improve in the build-up to the clash in Oita on Saturday.

England have not won a World Cup knockout game for 12 years.

But they have beaten the Wallabies in all of their last six meetings.

Defence coach John Mitchell told BBC 5 Live: "Billy's doing really well.

"He got through restricted training activity again today, ran with the ball, did some wrestling and boxing and some sprinting on the WattBike.

"He wasn't smiling after the WattBike, but he's in good humour and progressing nicely. At this point it's looking very likely."

Vunipola was likely to be rested had England's final group game against France in Yokohama last Saturday gone ahead as scheduled, rather than being cancelled because of the threat of Typhoon Hagibis.

But the loss of that game has bought him time, even as utility back Jack Nowell once again sat out training with a hamstring injury.

Mitchell said: "Billy is a very important player to us and a very likeable player as well.

"He loves the ball in his hand. He's very good at regaining and retaining momentum. He likes carrying the ball, which is where he has his greatest influence.

"He fits well within the team, but whoever gets the nods within the 31, everyone has a role to play."

England wary of adventurous Aussies

Australia were beaten by Wales in their key pool game and struggled in the first half against both Fiji and Georgia.

But they beat the All Blacks 47-26 in August, and in Michael Cheika have a coach who plotted England's demise in the group stages four years ago before taking his team on to the final.

Cheika has yet to settle on a preferred combination at 10 and 12, but with the form of muscular centre Samu Kerevi, he has one of the stand-out performers at this World Cup at his disposal.

Mitchell said: "The Wallabies are a very clever football team, and they will be clever at the weekend.

"They've always got their ability in terms of surprise, and they love ball in their hands, which is what they thrive on.

"You've got to look at how they attack - they love the ball in hand and they love putting width on it.

"Any one of those possible 10s and nines and 12s fall into that style of football. It doesn't matter who they put there, they can all play that style.

"Kerevi is such a strong character, and they tend to move him around in structured attacks. He looks like he's really enjoying his tournament, so he's a threat we'll need to be aware of.

"But we have our own beliefs in how we want to play, and we want to embrace this opportunity and bring our strengths out."

England's training was watched on Tuesday by Australian rugby league great Ricky Stuart, now the coach of Canberra Raiders.

Stuart will be invited to share his ideas about both coaching and England's shape in the run-up to a game that could do much to define whether the Eddie Jones regime has been a success or failure.

It is 12 years since England last reached the semi-finals of a World Cup, their defeat of a much-fancied Wallabies team in Marseille in 2007 one of their great displays in the tournament.