WELSH star Dan Biggar will be donning an Australian shirt as England face their do-or-die tie with the Wallabies at Twickenham.

A loss for England will all but dump them out of their own Rugby World Cup and write their names in history as the only hosts to do so in the history of the tournament.

It would be a result which would see Wales qualify, and the fly-half was bullish when talking about his alliance after his side's 23-13 win against Fiji on Thursday.

When asked if he had an Australian shirt, he said: "It'll be on Saturday, I promise you that.

"It's going to be a great spectacle and I'm sure England will come back strongly but I don't think there's any denying that I'll be supporting Australia on Saturday night.

"Looking at the pool at the moment, it reads pretty well for us "Hopefully we can get a good result on Saturday with the Aussies winning and that'll make it a bit easier for us."

The Osprey has not missed a kick yet in the tournament and hopes to keep his form going into next Saturday's clash with Australia.

He said: "It's going alright, so hopefully that doesn't jinx it now.

"I'm feeling good over the ball at the moment and it's always good to do your bit for the team and keep the score ticking over.

"In international rugby it's important to keep knocking points over so all-in-all it's going well."

Biggar's range has always been impressive, but he knocked over a 50m plus penalty against Fiji as well as a 49m monster to seal victory for Wales at Twickenham last week.

"Maybe it's just the emotion and the adrenaline when you're playing these big games - it always gives you a couple of extra metres," he said.

"I just stuck it down and tried to kick it as hard as I can - that was the plan for that one [Fiji kick]."

The victory leaves Wales sitting pretty on top of Pool A with three wins from three, and Biggar said: "I think we deserve a fair bit of credit for grinding it out against a Fiji side who were fresh and full of great players.

"I don't think for one minute we expected to come here and for Fiji to allow the floodgates to open and for us to score 40 or 50 points.

"Fiji pushed England all the way in the first game, Australia didn't get a bonus point against them so we knew how difficult it was going to be.

"I think we deserve a bit of credit for just getting through it and putting ourselves in the position we're in.

"We tried to keep the ball tight early doors in terms of our driving game and our pick and go game but fair play to them sometimes it doesn't work out and that's when they come alive from turnovers.

"Sometimes we'd turn the ball over then they'd turn the ball over so it was all a bit frenetic.

"There was a period in the second half where we kicked a bit of ball away from turnovers too much - myself included - so there's always things to work on but overall I thought we were pretty good.

"It was a solid performance to get a victory."

Warren Gatland's men faced a five-day turnaround following their heroics at HQ, and it took its toll on his players.

Biggar himself limped off with cramp and Bradley Davies, Dan Lydiate and Matthew Morgan all suffered minor injuries.

Talking of the back-to-back games, Biggar said: "It's massively difficult.

"From the magnitude of the game on Saturday where the boys were on a serious high through to Sunday we said it was a great victory, but it's one we've got to park now because it's just one pool game.

"The focus was on Fiji on Monday morning.

"It was a tough five-day turnaround so I've got a few bumps and bruises and hopefully I can get back to training on Monday and I'll be good to go."

One man who will be hoping this is the case is his kicking coach Neil Jenkins and the former record points scorer believes the best is yet to come from Wales' World Cup playmaker.

"From a young age you could tell Dan was going to play for Wales," said Jenkins, skills coach and his country's record points-scorer.

"He would probably have told you straight away he was going to be a Wales international and a British and Irish Lion. I am sure that is on the horizon.

"He has matured over the last few years and is playing so well. When you see him playing in the PRO12, he actually makes it look easy.

"I think the next level was for him to dictate like that in a Welsh shirt, and I think he has done that.

"He is a massive player for Wales at this moment in time and a real go-to man. He has taken the team by the scruff of the neck and he makes good decisions.

"I think there is a lot more to come from him yet.

"He has only really come to the fore since 2013, yet he was really unlucky not to have gone on the Lions tour (to Australia) that year. But there were quite a few good number 10s at that time.

"He didn't really play in 2014, but he has come back in this last year and has been exceptional. He is only going to get better.

"I wouldn't say he is too far away from being one of the best 10s in the world. I think he has the desire to be the best in the world, and he is certainly going the right way about it."

Wales look to have emerged injury-free from what Jenkins described as a "brutal Test match" against Fiji after seeing their World Cup campaign scarred by injury setbacks - head coach Warren Gatland has lost the services of original squad members Leigh Halfpenny, Scott Williams, Rhys Webb, Cory Allen and Hallam Amos.

"We will be okay," Jenkins added.

"We have got a nice turnaround, and the boys can look forward to this weekend and then look forward to a big Test match against Australia next weekend.

"It was a brutal Test match last night. We have got the job done and we have won and we can look forward to the game next week."

Attention will now turn to Twickenham tonight, when England know they will be knocked out just 15 days into the tournament if Australia prevail.

"I am not going to be at Twickenham," Jenkins said. "I will be watching it in the house.

"We get enough in terms of analysis with all the cameras and views we get. So, it is a lot easier to stay around here, feet up and look forward to tomorrow's game.

"What will be will be. Whatever happens tomorrow night, we have got to turn up a week on Saturday and win.

"Even if England did lose tomorrow night and go out, we will still be looking forward to the Australia game.

"It's a game we want to win because we want to go through as group winners. I think the focus for us is on a week Saturday."