Castres lock Richie Gray has agreed a four-year deal with Top 14 rivals Toulouse.
The Scotland international, who helped his country reach the quarter-finals of the Rugby World Cup, made the switch to France from Sale Sharks two years and will be on the move again at the end of the season.
Gray said he was unable to ignore the overtures of the four-time European champions, who sit second in the Top 14 table and occupy the same position in European Champions Cup Pool One.
"This was a very difficult decision to make, I have loved my time in Castres, the club and the supporters have made my time here very special and I will leave with very fond memories," he said.
"However the opportunity to play for one of Europe's most successful clubs, steeped in history, is an incredible one for me.
"When I met with the club they described their ambition and I felt this was the right move for me, to challenge myself in what is a very strong squad.
"I still have seven months here at Castres, I will give everything I can to the club in hope of achieving top six and then who knows.
"My goal for now is to leave Castres on the best possible note, I will give everything I can to the club, the players and the coaches."