Martin Johnson has warned England must be as mentally sharp as they are physically tough if they are to combat the unpredictable French in Saturday's Rugby World Cup quarter-final.
Johnson knows from experience France can veer from being a rabble to world-beaters in the space of a week, sometimes in the space of the same match. Marc Lievremont's squad have appeared to be divided and in a state of disarray since last weekend's defeat to Tonga - but that is not necessarily to England's benefit.
Johnson said: "We know France can under-perform but we also know they can produce games that are almost unstoppable, as we have seen at World Cups. You absolutely expect anything and for it to be of the highest standard. Anything can happen and we have to deal with it mentally. If you don't deal with it mentally you can't deal with it physically."
While England may not have traditionally been the most adaptable of sides, they have shown their mettle by coming from behind to beat both Argentina and Scotland so far at this World Cup.
Captain Lewis Moody said: "It is certainly a confidence-builder for the squad to know that when you are behind you can close games out. The most important thing for a team is to win no matter what the game has been like.
"When you have the Chris Ashtons, the Jonny Wilkinsons, the Toby Floods, the Ben Youngs, the forward pack - you have the arsenal there to take that victory."
Wilkinson has confirmed a final decision over whether he or Flood will kick will be made after a practice session at Eden Park.
If England can beat France for the third successive World Cup, they will meet either Ireland or Wales in the semi-finals.