Martin Johnson insists England's path through the toughest group in World Cup history is fraught with danger, but believes the rewards will be great if they progress as winners.
The enormity of the challenge facing the tournament hosts in Pool A was laid bare last week following Australia's Rugby Championship title triumph and Fiji's success in the Pacific Nations Cup.
On three consecutive weekends, England must dispatch Fiji, Wales and Australia if they are to be offered a route through the less arduous half of the World Cup draw, avoiding New Zealand and South Africa.
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If they do advance into the knockout stages, Johnson predicts they will benefit from having been battle hardened against high-calibre opposition.
"It's the toughest pool there has ever been in a World Cup and someone will be going home early," Johnson told Press Association Sport.
"Whoever loses England v Wales, their next game becomes a must win. They'll have to beat Australia just to stay in the tournament.
"But in a way it won't do England any harm at all. It's often the teams that have to fight and battle who will be in the best position come the end of the World Cup. If they win the group then it doesn't really get any harder, at least until the final."
Australia's visit to Twickenham on October 3 is already looming large in English minds with Red Rose forward coach Graham Rowntree revealing on Tuesday that 'we're watching them constantly as a group, that country are going places'.
Johnson, captain of the England team that won the 2003 World Cup following a 20-17 victory over the Wallabies in the Sydney final, views them as the most dangerous team on the global stage.
"Australia can be utterly lethal when it comes to scoring tries out of situations where there's nothing on, more so any other team in the world," Johnson said.
"They execute with their hands very, very well and suddenly they're in. They score tries and that makes them lethal."
"People perceive they have weaknesses here and there, but they're usually able to cover them up. They almost won a World Cup in 2003 when they couldn't really scrummage.
"If England get ascendancy in the scrum and the referee penalises Australia, it makes a big difference to the game. If he doesn't penalise, then it nullifies the advantage at the scrum."
Johnson insists England dare not look beyond the curtain raiser against Fiji, who toppled Samoa last week to be crowned Pacific Nations Cup champions, at Twickenham on September 18.
"It's a perfect opening game for Fiji because while everyone is talking about England, Wales and Australia, they'll be thinking 'whoa, don't forget us, we can play a bit too'," he said.
"And that opening match is always a tough one. In 2007 France lost as hosts, albeit to a very good Argentina side.
"If England go behind against Fiji, the crowd gets a bit nervous and the players get nervous, you have to keep your head and keep playing. Teams like Fiji with nothing to lose are very difficult in those situations.
"It starts from the first kick off in England's pool because there's no room for manoeuvre, you must hit the ground running."
Martin Johnson is a MasterCard brand ambassador for Rugby World Cup 2015. MasterCard will be delivering Priceless Surprises to MasterCard card holders and rugby fans around the world.
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