Black (right) and Wilkinson have a long working relationship

Both Black and the club say they will make no further comment on the matter.

Black's exit is a surprise considering his close and lengthy working relationship with England and Newcastle fly-half Jonny Wilkinson.

The pair have worked together since Wilkinson, 28, was 17, and Black has had two spells at Newcastle, while also being involved with the Lions.

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, a former Newcastle nightclub doorman, began his top-flight coaching career in football with Newcastle United under Kevin Keegan.

He then switched to Newcastle Falcons where his exploits attracted the attention of then Wales coach Graham Henry, who is now in charge of New Zealand.

Black then travelled with the British Lions on their tour of Australia in 2001.

He has also worked in football with Fulham and Sunderland as well as with boxer Glenn McRory and former Olympic triple jump gold medallist Jonathan Edwards.