And further raids are expected, with Greg Inglis, Israel Folau and Johnathan Thurston all said to be in the sights of French agents.

Williams stunned Bulldogs officials yesterday when he flew to France to explore a two-year, $3 million offer to join a French club, believed to be Toulon. The Kiwi superstar was spotted at the airport yesterday and fled without a word to Bulldogs management.

But late last night Toulon denied they had signed Williams.

Mourad Boudjellal, Toulon's president, said Williams and the club had spoken a while ago but there was no deal. "We did make contact some time ago with Sonny Bill Williams," Boudjellal told AFP from Miami. "He said to us that he wanted to move from rugby league to union but that is where it finished.

"I cannot confirm what was on Canterbury's website. However, I deny that it is true."

The Sun-Herald has learned that Mason, meantime, was offered $2.5 million over two years to join his former teammate in France.

"There's been a bit of interest but I'm honouring my contract to the Roosters," Mason told The Sun-Herald last night. "I'll be here till 2010. They've shown interest, but I'm very happy here."

Bulldogs coach Steve Folkes was stunned when told Williams had fled. "It's very unexpected," Folkes said. "My first concern is finding someone tomorrow to play in his spot [against St George Illawarra]."

The Sun-Herald broke the story in May that Williams would walk out on the Bulldogs, but the club was confident the issues behind his desire to leave had been resolved.

The Bulldogs were wrong.

Williams left Sydney with the brother of his manager, Khoder Nasser, on what is believed to be a one-way ticket to Europe.

Those close to the 22-year-old say Williams has tired of the media scrutiny involved with being an NRL star and is unhappy with the direction the Bulldogs are heading in.

A source close to Williams also said he had an ongoing back complaint and was unhappy with how the club had managed it.

He was also upset with what he perceived as excessive media scrutiny into his private life and, at the urging of the club, having to admit he had problems with alcohol last year.

The shock walk-out is sure to spark a legal stoush. Bulldogs officials are confident there is no get-out clause in his contract.

Williams has four years to run on the $450,000-a-year deal with the Dogs and a lot of the club's marketing revolves around him.

"It just defies logic, it really does," said Bulldogs chief executive Todd Greenberg, who was informed of Williams' departure by Nasser. "For a 22-year-old to pick up and go, it's a big call. It's unacceptable to walk out on a contract - it's unacceptable to your teammates, in particular. As a minimum, all fans deserve an explanation. We've all been let down."

The Bulldogs were last night looking to put an injunction on Williams to prevent him from playing in any rival team or competition.

"We're looking to take out an injunction which will stop him playing for anyone else, any code or any club," Greenberg said. "I'm determined to ensure if he's not playing for the Bulldogs, he's not playing at all. Full stop."

There were early suggestions that Williams could have problems getting registered in France.

The cut-off point to register players is July 14 - the same stumbling block that prevented Mark Gasnier from playing there last season when he wanted to leave St George Illawarra.

Previously there had been rumours he had signed on July 9.

Revelations that the club's biggest drawcard has left have outraged fans and confirmed that French rugby clubs are serious about poaching the best stars in rugby league.

Gasnier and Craig Gower have already signed with French clubs, while Newcastle's Adam MacDougall is set to leave league.

Williams's move is an even bigger slap in the face to the club and supporters considering the lengths Greenberg had gone to to keep his superstar happy. Only last weekend, the Bulldogs opened up the gates for free to the Polynesian community at Williams's request.

"I had lunch with Sonny on Thursday and we spoke at length about our plans for 2009," Greenberg said. "I'm as shocked as anyone."

NRL chief executive David Gallop described the situation as "unacceptable". "It is unacceptable to walk out on a contract," he wrote. "If he has personal issues we are happy to discuss them with him. We will support the Bulldogs to enforce the contract and prohibit Sonny Bill from playing for any team other than the one he is contracted to."

News of Williams's decision was treated with disbelief in New Zealand. Former Manly fullback Matthew Ridge said: "It's pretty immature. I honestly can't believe this news. Sonny Bill appears to have changed from a fiercely loyal Bulldog to [someone] who is looking out for himself and the big dollars."

Former Wallabies coach John Connolly, who last week wrote in The Sun-Herald of the danger French rugby posed to the NRL said: "My first reaction was that it can't be true. Contractually it just can't happen unless someone at the club told him that yes, you can go or unless he hasn't been paid third-party money or something like that, it just can't happen.

"I think it is pretty bad form from Sonny Bill. These guys, these highly paid young guys, just seem to have a different set of loyalties and values. It's all about the dollar. Every manager worth his salt will be trying to get his player over there now."

Phil Gould, who has been criticised for warning the NRL of the possible loss of the likes of Williams to overseas, offered just one quote last night: "I told you so."