The retired businessman passed peacefully in his sleep on Sunday 30 July, according to colleague Brian Smith.
Clark joined London-based John D Henderson in 1936, becoming director in 1957 until he retired in 1980 as the company celebrated its 100th anniversary before it was sold off in 1986.
Speaking at his retirement lunch as reported by Paper UK News, Clark said: "One thing I have learned over the years is that you never let people down.
"Give them a date and stick to it; if for some reason you can’t make that date then be frank about it."
Clark also recalled the days when Upper Thames Street was "the street of paper" and three-wheeled trollies delivered orders in his early days with the company.
He was awarded the Distinguished Flying Cross for his services in the RAF during the Second World War.
Clark moved to Sidmouth in Devon with wife Wynne upon his retirement and leaves behind a son, Graham, four grandchildren and 14 great-grandchildren.
Brian Smith, who was managing director at John D Henderson, said: "Leslie was a very able director and well-known in the trade."
