Mr Grunfeld continued to attend the office regularly as a consultant until last week, when he was said by a colleague to be "in good form".
He first met Mr Warburg in Holland in 1935 after he fled his native Germany. They promptly launched a merchant bank in London called New Trading Company, later SG Warburg. Mr Grunfeld built the corporate finance side of the bank and took over its chairmanship when Mr Warburg retired in 1969.
Mr Grunfeld favoured the merger with Swiss Bank Corporation (SBC) in 1995 over the failed merger with Morgan Stanley. He remained a consultant to Warburg Dillon Read (WDR).
Marcel Ospel, chief executive of WDR's owner UBS, paid tribute, saying: "I was always impressed by his depth of experience and understanding of people, and personally enjoyed his kindness and keen wit."
Sir David Scholey, for many years Warburg's chairman, said: "He was not only a great banker and a great friend, but as the co-founder of SG Warburg... he made a unique contribution to the City and international finance."
Lord Roll, who succeeded Mr Grunfeld as chairman in 1974, remembered his sense of humour. "Two days after I joined the firm I had to go to Stockholm in connection with my earlier work. Henry said: `While you are there, why don't you arrange for a merger between Swedish Match and Imperial Tobacco?'"
Another colleague recalled a remark after Mr Grunfeld had both knees replaced three years ago: "The knees are fine - it's just everything else that needs replacing now."
Obituary, Review page 8