This is a fascinating article and deserves close attention in total. What follows is a excerpt.

Yorkshireman behind All Blacks’ downfall prepares for Le Crunch
France’s defence coach, David Ellis, tells William Fotheringham why Brian Ashton should be worried
Wednesday October 10, 2007, The Guardian

The spectacular victory over New Zealand that earned France a semi-final place against their old enemies from this side of the Channel was, ironically enough, “made in England” - with one of the keys to the upset in Cardiff being the steadfast rearguard masterminded by their Yorkshire-born defence coach David Ellis.

The official post-match statistics, somewhat impromptu in their nature, did not actually do justice to France’s achievement in restraining an All Blacks side that spent long spells in their 22 - at one point managing over 30 consecutive phases of play in a lengthy close-quarters battle - and enjoyed almost three-quarters of possession.

According to Ellis’s own statistics, France made a total of 299 tackles, their highest in any match under the Yorkshireman. Critically, they missed just 15. “That’s around five per cent, normally you would look for about nine per cent missed so that’s as good as it gets,” he said. Such is the Ellis effect that the staunchest defender of them all was the Toulouse back-row forward Thierry Dusautoir, who is only at the World Cup because of an injury to Elvis Vermeulen, the author of 38 tackles.
…
What mattered as much as the tackles themselves was the target of the tacklers. Critically, Ellis said yesterday, France’s tacklers were instructed not to go for All Black legs but to tackle around the upper body, in pairs if possible, in order to prevent the quick off-loads that had given New Zealand such impetus in the past.

“They had perfected off-loading and it was unstoppable,” said Ellis. “We knew we had to stop the off-loads. We weren’t putting them to ground. If you put them to ground with leg tackles, they have a system where they have a support runner who is always behind the player being tackled.

“The ball carrier goes into contact, the support runner comes over the top, takes the second tackler out, there is a third support runner just in case, [the scrum-half] Byron Kelleher gets the ball and it is gone. It’s a two-man ruck. There was no point in putting them to ground close to the gainline because we’ve got to come back on side, going backwards a metre at a time.

“If we block the off-load, they are in a foreign situation, the ball is slowed down. [The French players] can block it. There were several occasions in the second half when [Frédéric] Michalak hit the guy, Jauzion was in next, we were in, we kept them on their feet, the ball is off the ground, they’ve taken it into contact, scrum for us. They can’t put two men into the ruck, they put five men, their whole structure has gone completely.”
…