Newcastle Falcons prop Carl Hayman will make the switch to fellow Amlin Challenge Cup quarter-finalists Toulon at the end of the season.
His side could still meet the French in the semi-finals of Amlin Challenge Cup should they beat Cardiff Blues and the Scarlets in their respective semi-finals in April.
The draw will take place after Falcons and Blues complete their match on Sunday, April 11.
Hayman, who has made 60 appearances for the Falcons in his three year stink at the club said: "This has been one of the hardest decisions of my life.
"I have enjoyed my time immensely here at Newcastle Falcons, a great club blessed with fantastic supporters. I would like to thank the club for being so professional in the way they have allowed me the time to make my decision."
Falcons chairman Dave Thompson said: "Carl has given outstanding service to Newcastle Falcons during his time here."
The 30-year-old prop has made a total of 60 appearances for the Falcons since joining in November 2007.
Thompson admitted he wanted the former All Black to stay on at Kingson Park. "We held numerous serious discussions about extending his stay with us and made him our best possible offer, but ultimately we respect his decision and wish him every success for the future," he explained.
"Carl remains 100% committed to the Falcons for the remainder of the season, and as club captain continues to have a vital role in firstly maintaining our Guinness Premiership status, and secondly helping us to achieve our ambitions of Heineken Cup rugby for next season.
Falcons director of rugby, Steve Bates, said: "Carl has been an outstanding player and leader for us during his time at the club.