The football world was saddened on Saturday by news of the death of Charlton at the age of 86.
In a 17-year playing career with the Reds, he played 758 games and scored 249 goals, winning countless domestic honours as well as famously lifting the World Cup with England in 1966.
He was a figure who, in many ways, transcended football and was admired for his grace and goals on the field as well as his values and standards off it.
Ahead of the 191st Manchester derby between United and City on Sunday, it was fitting that Guardiola penned a personal message in the book opened for the football icon.
Guardiola’s signing of the special book to remember Charlton comes just 24 hours after City ambassador Mike Summerbee OBE offered his own respects.
Summerbee, who came up against Charlton in Manchester derby encounters of the late 1960s and early 1970s, visited Old Trafford to showcase his appreciation and admiration for the United great.
“What represents us is Mike Summerbee going to Old Trafford to sign the book on behalf of Man City,” said the boss.
“We have a huge respect for Manchester United and we prove it, losing and winning these years. We have a lot of respect and especially the icon, the figure of Sir Bobby Charlton.
“We will be part of the condolences for the family, Manchester United and English football. We will be there.”
