Wales and Australia have locked in quarter-final berths after they both toppled World Cup hosts England in the pool stages.

They will clash at Twickenham on Saturday to decide which team finishes at the pool dubbed the "group of death" before the tournament began.

Australia, Wales and England were all ranked inside the top six in the world, but only two were able to advance to the next stage of the competition.

World Rugby did the World Cup draw three years ago to plan for the tournament.

"It's not just the group of death, it's the group of hell," Gatland said on Sunday (Monday morning AEDT).

"Everyone is talking about England as the first host country to miss out on the quarter-finals but the stupid thing is why was the World Cup draw done three years ago? It's ridiculous. If they had followed the football model then we wouldn't be in this position."

Gatland said knowing his team had already qualified for the next stage would allow them to "take the shackles off" when they play against the Wallabies.

Australia are unbeaten in their last 10 Tests against Wales, a streak stretching Gatland's entire Wales coaching stint.

"We always planned to make the quarter-finals," Gatland said.

"We knew how tough this group was going to be, not with just England, Australia and ourselves, but Fiji, too. I think if Fiji had been in other groups they would have qualified for the quarter-finals as well."

"So to have qualified now gives us the opportunity to take the shackles off a bit and to start focusing on winning the group.

"We are delighted to be through and Australia have done us a massive favour. You've got to feel for other teams involved. There is a huge amount at stake, with families and livelihoods, so I am just trying to keep things in perspective."

England coach Stuart Lancaster is under the pump and faces a fight to keep his job after the unenviable feat of helming the first host nation in World Cup history to be knocked out of the tournament in the group stages.

World Rugby officials say the draw process would be reviewed after the tournament.

But Wallabies coach Michael Cheika did not want to be drawn on the way teams are put together in groups.

"It's got nothing to do with me, I'll be honest I don't even know how it's done," Cheika said.

"I don't know how these teams managed to get into the pool together, I wouldn't have a clue. I didn't really know about it, I wasn't even looking at it."