Matt Giteau will land the biggest guilt trip in rugby history on Jonny Wilkinson if Australia dump England out of the World Cup at the first hurdle.
Giteau picked ex-Toulon team-mate Wilkinson's brains for tips on how to win the World Cup - and now wants that information to come back to haunt England's poster-boy former fly-half.
Wallabies playmaker Giteau revealed Wilkinson has been cancelling his calls this week, ahead of England's do-or-die battle with Australia at Twickenham on Saturday.
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Giteau mined 2003 World Cup-winner Wilkinson for information on how to lift the Webb Ellis Cup, and is ready to put those trade secrets to good use this weekend.
"I'd make him feel guilty - I'd make him feel really guilty," said Giteau of exploiting Wilkinson's help.
"He won't answer my calls this week, and I've tried him a lot!
"He won't answer me this week, maybe next week."
Beleaguered head coach Stuart Lancaster's England tenure is on the line in Saturday's nerve-jangling Wallabies clash, where defeat could end the hosts' quarter-final hopes.
England would become the worst-performing host nation in World Cup history should they fail to progress from Pool A to the last eight.
Lancaster's men lost out 28-25 to Wales last weekend despite twice leading by 10 points, confirming the hosts' worst fears about contesting the 'pool of death'.
Wilkinson drove England to World Cup glory in the 2003 final with a 20-17 victory over Australia that crushed the hosts, Giteau included.
The 32-year-old Australian pivot was also outfoxed by England and Wilkinson in the 2007 quarter-final in France, Brian Ashton's side victorious 12-10 in a sun-drenched Marseille.
Giteau fully expected his Wallabies career to be dead and buried when axed from the 2011 World Cup squad, cementing his decision to move to Toulon.
New Wallabies boss Michael Cheika forced an alteration to Australia's selection policy on overseas-based players however, ushering Giteau and Toulon club-mate Drew Mitchell back into the fold.
The last time England played Australia at Twickenham, Giteau was drinking beer in corporate hospitality with Mitchell - now both men will be vying to spoil the hosts' party.
"I was over having a few beers with Drew," said Giteau, of England's 26-17 victory over Australia at Twickenham in November.
"Watching it had been maybe my third year not playing international rugby so it was normal for me, just like going to any football game and watching it as a supporter, that's where my mindset was at.
"I just went to watch the boys, the atmosphere and see the game on the other side of the fence.
"When I was having a few beers, it never crossed my mind that they might relax the rules. The rules were in place as they were, so at that point it was just really we had a break from Toulon."
"I'm massively more appreciative of it all now that I'm back with Australia. I suppose I am more grateful than I was.
"When you're playing consistently I think you take it for granted - it's a shocking thing to take it for granted, playing for your country.
"But now that I've been given a second chance... little things like getting your kit again make you feel 19 like when it all started. I certainly take nothing for granted now.
"In the 2007 quarter-final against England I just remember we maybe tried to play too much, on a really sunny day.
"We were taught a lesson in tactics by that goal-kicker, I can't remember his name!
"We were outplayed that day. And it just shows what you need when you get to that part of the competition. One game and you're gone.
"Even now one game for us could be a huge turning point."