Saracens have agreed a deal to sign Northampton Saints flanker Calum Clark.
Clark will move to Allianz Park from the Saints in time for the beginning of next season.
The England international has put pen to paper on a three-year contract and becomes Saracens' third signing for the 2017/18 campaign.
The Aviva Premiership club have already agreed deals for Wales international Liam Williams and Toulouse hooker Christopher Tolofua to join in the summer.
Despite his departure being confirmed, Clark insists he will continue to give his best for the Saints.
"I am very fortunate to have played for a great club like Northampton. I've had a difficult 18 months on and off the field and I feel like I need a new challenge," said Clark.
"As ever, I am fully committed to playing to the best of my ability for the remainder of my time at the club.
"I feel very privileged to have been given an opportunity at Saracens. They are always a difficult side to play against and I'm looking forward to taking on a new environment and getting a fresh start in the summer."
Since making his debut for Leeds a decade ago, Clark has established a reputation as one of the league's finest back row forwards.
He moved to Northampton in 2010 and has gone on to represent England Saxons and England during his time at Franklin's Gardens.
Saracens director of rugby Mark McCall said: "Calum is a very talented player and will fit in brilliantly here. He is still a player with a huge amount of potential and in our opinion he has his best years ahead of him.
"We're looking forward to welcoming him to the club later this year. We're very happy to secure Calum's signature, along with Liam's and Christopher's, as we continue to build for the future.
"We have identified a handful of players who we felt would improve what is now a stable, successful and developing squad and we're delighted to have been able to wrap up these signings for next season."