Charlton was a key member of England’s victorious 1966 World Cup team and also enjoyed great success at club level with United, who became the first English club to win the European Cup in 1968.
Born in Ashington on October 11 1937, Charlton made his debut for United in 1956 and went on to play 758 matches for the Red Devils, scoring 249 goals.
He won three league three titles and one FA Cup at Old Trafford and, after leaving United in 1973 and becoming Preston manager, he returned to Old Trafford 11 years later as a club director.
His family announced on Saturday afternoon (October 21) that he had died peacefully in the early hours of the morning surrounded by his family.
John Gregg passed on his condolences to the Charlton family and revealed he only found out the news after watching Glentoran - where he is a coach - beat Glenavon at The Oval.
"It is sad news and I knew nothing about Sir Bobby potentially passing away or anything like that," he said.
"I was in the changing room delighted with how we played and I was asked to do an interview for the radio which I thought was bizarre.
"It was then I was told that Sir Bobby had passed away and it completely knocked me back.
"I was asked a few questions and I became emotional because he played with my dad and they went through so much together.
"It wasn't uncommon back then for guys like Sir Bobby to be in my house as the players were great friends outside of football.
"In world football terms, Sir Bobby was one of the football Gods and was the most lovely and normal man you could ever meet despite his stardom on the pitch."
Charlton’s European Cup success at United came 10 years after the Munich air disaster, which he and team manager Sir Matt Busby survived but which claimed the lives of eight of Charlton’s team-mates.
Gregg pulled him and other passengers from the plane's burning wreckage and John believes this act of heroism helped set the "foundations" for Manchester United moving forward.
He added: "My dad and Bobby were the last two survivors of those who were on the plane in 1958.
"I have never spoken much about the crash but the bond created from that heartbreaking disaster will never be broken and it helped set the foundations for Manchester United and the fabric of the club so to speak moving forward since that tragedy.
"Sir Alex Ferguson phoned me when my dad died to pass on his condolences and told me that representatives from Manchester United will be at the funeral.
"I knew Sir Bobby hadn’t been feeling well at that time but I got word that he was on the flight and it showed you just how much my dad meant to him as he could have easily stayed at home to recover.
"His presence helped us as a family as he and my dad were very close, and I remember going to Sir Bobby’s soccer school in Manchester as a seven or eight-year old.”