Steve Black, the highly-respected fitness and conditioning coach, has left his position at Newcastle with immediate effect.
The decision was taken in a meeting this morning and Black leaves Kingston Park "by mutual consent".
Black’s departure is a blow for Newcastle given his reputation as one of the most inspirational coaches in the game.
It could be significant for Newcastle and England fly-half Jonny Wilkinson, for whom Black has been a mentor throughout his career.
Wilkinson once said: "I trust him with everything. He’s the driving force behind my ambitions. Much of my confidence and self-belief comes from my respect and belief in him."
Black guided Wilkinson through three tortuous years as the England fly-half was laid low by a succession of injuries following the 2003 World Cup.
A former nightclub bouncer, Black worked under Graham Henry for Wales and the 2001 British and Irish Lions.
He has also enjoyed stints in football with Newcastle, Fulham and Sunderland and worked with former world cruiserweight champion Glen McCrory.