Manchester City assistant manager Arthur Cox has announced his retirement, ending his long association with Kevin Keegan.
Cox, 64, signed Keegan as a player for Newcastle, and returned to work under him when Keegan managed the Magpies.
Former Derby boss Cox then followed Keegan to Fulham and was a coach in Keegan's England set-up.
Cox said: "I have made this decision in the best interest of Manchester City and Arthur Cox."
Keegan also paid tribute to the man he described as a "true friend and confidante."
"Arthur Cox has been a wonderful servant to football and a great influence on my managerial career.
Cox was part of Sunderland's 1973 FA Cup triumph
"I owe him so much, I hope he
enjoys his retirement to the full.
"If anybody deserves a break and a bit of time with his family it is Arthur.
"I understand his reasons. He is a one-off and we will stay friends for life."
Cox began his coaching career with Coventry after his playing days with the midlands club was cut short by a broken leg.
He had coaching stints at Walsall, Halifax, Preston and Aston Villa and was
assistant manager at Sunderland when they beat Leeds in the 1973 FA Cup final.
Cox was also an assistant at Galatasaray in Turkey and in 1976 he landed his
first management job when he took charge of Chesterfield.
He took over at Newcastle in September 1980 when they were in the old second division.
But his signing of Keegan as a player proved inspirational as he sparked the Geordies to promotion to the top flight in 1984.
Cox caused a shock on Tyneside when he left to manage Derby where he stayed for nine years.
ARTHUR COX'S CAREER
1976: Appointed Chesterfield boss
1980: Named Newcastle manager
1982: Signs Kevin Keegan for Newcastle
1984: Guides Newcastle to promotion, leaves to manage Derby.
1993: Named Keegan's assistant at Newcastle
1998: Follows Keegan to Fulham
1999: Becomes part of Keegan's England set-up
2001: Follows Keegan as assistant at Man City
When Keegan returned to Newcastle as manager in February 1992, they were facing the drop into the third tier for the first time in their history.
After keeping them up Keegan again brought in Cox as his assistant and they swept Newcastle into the Premiership the following season.
When Keegan went to manage Fulham, Cox followed him to Craven Cottage as director of football.
Keegan again called on his trusted right-hand man when he became England coach and it was no surprise that he appointed Cox as his assistant when he took over the reins at Manchester City.