Chris Robshaw has urged England to display a clinical edge in Saturday's RBS 6 Nations title decider against Wales at the Millennium Stadium.
England laboured to an 18-11 Twickenham victory over Italy last weekend, with clear scoring chances wasted during the first half, especially.
If England are anything like as lethargic today, then title holders Wales could have a field day as they target a 12th win in their last 14 Six Nations Tests.
"When you come to a place like Cardiff, you might get one or two chances, and we've got to make sure we are good enough to make it count, whether it is the first minute or the 80th minute," England captain Robshaw said.
"It is one thing saying it and it is another thing doing it. That is the challenge we have.
"Of course, everyone wants to go out there and win, but it is about how you go about it and breaking it down into the smaller, finer detail.
"We can't afford to switch off at all or lose concentration or lose our composure. If we get a chance in the first or 80th minute we need to be mentally prepared and right up for it.
"It's a huge occasion for English rugby, and there is a massive opportunity out there for us if we can go out there and hopefully deliver on what we've talked about."
The tournament's only remaining unbeaten side are one more victory away from emulating 2003 World Cup stars like Martin Johnson, Lawrence Dallaglio and Jonny Wilkinson and conquering all before them in Europe.
And the fact it could be achieved less than 18 months after a World Cup debacle in New Zealand merely underlines the magnificent work done by Robshaw and England head coach Stuart Lancaster since they took office for last season's Six Nations.
Wales, though, could easily spoil the party, with a win or draw denying England the Grand Slam, while victory by seven points or more would mean Six Nations silverware remaining in Cardiff.
"We know what happens if we win, and we know what happens if they win," Robshaw added.
"Both teams know exactly what they want to get out of this game and it is about showing that intent from the off. Both sides will want to get off to a great start and build momentum from that.
"We've been to intimidating places before, the likes of Ellis Park (in Johannesburg), and Wales is definitely up there. People speak about it as probably one of the best places to actually go and play rugby.
"If you give the crowd an opportunity to get into the game in the first 10 minutes, then it's going to be a long old afternoon, as we found at Ellis Park (last summer), when we were 20 points down in 20 minutes.
"It is about making sure that in the warm-up we soak up what it is going to be like, and make sure when that first whistle goes we are mentally prepared and ready to give it our all."
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