Relegated Super League side London Broncos have signed Catalan Dragons half-back William Barthau on a two-year deal from the start of 2015.
The 24-year-old, who has won eight international caps for France, has made 16 appearances for the Dragons.
"It will be good to learn a different system and to play with different players," he said.
"I'm really motivated to be part of a winning culture and I'm also looking to improve individually."
Barthau hopes he can help the Broncos secure promotion from the Championship during his time in the capital.
"The challenge is to get into the top four and then play four Super League clubs to show we are ready to play in Super League again," he said.
"I know that I can play my part in helping the club achieve this."
Herold has a broken arm and is set to return to France.