England manager Martin Johnson says World Cup quarter-final opponents France should not be underestimated.
Les Bleus made the last eight despite being beaten 19-14 by Tonga, while England struggled to a 16-12 win over Scotland to secure top spot in Pool B.
"France are dangerous and are never more dangerous than when they're flying under the radar," said Johnson.
"It will be knock-out rugby and it is certainly a big step up in terms of the opposition we are facing."
England needed to beat the Scots or avoid being beaten by eight points or more to book their last-eight tie in Auckland next Saturday.
But Johnson's side were behind from the ninth minute until the 77th, when Chris Ashton crossed for a converted try to give them victory.
"We kept our nerve in the end and got it won. It's never dull," said Johnson.
"We got on top in the second half. We didn't always get rewards but we kept hammering away."
Scotland were the better team in the first half and led 9-3 at the interval, which they extended to 12-3 after 55 minutes.
"It was a bit like the Argentina game - we gave away lots of free-kicks and penalties, the set-piece creaked, we couldn't get a foothold in game," noted Johnson.
"When we did we got penalties 30, 40 yards out - they were tricky kicks.
"We didn't get an opportunity to attack them that much, they had the initiative in the first half, but we felt if we could hold onto the ball then we could create chances.
"Six points down in a game like this is tough but actually the guys handled it really well."
Jonny Wilkinson - who missed four kicks out of six at goal - landed a smart right-footed drop-goal after 57 minutes before his second penalty on the hour brought England to within three points.
Wilkinson was forced off with five minutes left with a blow to his forearm - he will undergo a scan on Sunday. Toby Flood, who had earlier come on for Mike Tindall, switched to fly-half and conjured the winning try for Ashton.
"There is a lot to get better at," Johnson added. "We're making it very hard for ourselves at times. But the main thing is the character we showed to get out of a hole. Whoever scored the first try today was going to get across the line - we kept our nerve, got on top of them, and finally got our reward for it.
"The game isn't always going to be beautiful. It was chaos out there. But we finished it off."
England captain Lewis Moody was full of praise for the Scots after what he described as an "incredibly tough day".
"Full credit to Scotland, they played a fantastic game," said the open-side flanker.
"We knew they would and we didn't make it easy for ourselves by any stretch of the imagination with the penalty count and not keeping hold of the ball.
"But we can only win the games in front of us and we've done that today. It's another win - that's all we're here for and that's all that matters."
Wing Chris Ashton, whose match-winning try was his sixth of the tournament, the most any Englishman has scored at a World Cup, admitted England had left it late to "dig themselves out of a hole".
"Three points down with a few minutes to go, we were certainly cutting it fine, but we managed to get there," he said.
"It is a harsh way for Scotland to go out of the competition and I am sure they are not taking it well.
"I thought they did a great job. But we have been in that position a few times before and you learn from it. It is always good to get yourself out of a hole.
"It came together in the end but we just need to get there a bit earlier. We need to be better than that next week."
Aside from Wilkinson's injury, England will also be sweating over a potential citing for wing Delon Armitage, who caught Chris Paterson with a high tackle.