Inchbald, who was president of the IPR from 1969-70, was also announced as a founding fellow of the Public Relations Consultants Association (PRCA) in April 2010.
Grayling chief executive Alison Clarke, who worked for Inchbald at Welbeck, said: "Denis was really committed to professional standards in the industry which is why he was so supportive and involved in the IPR and the PRCA. He actively encouraged my involvement, which in turn has led to my own active involvement in both bodies."
Ann Brunton, who co-founded Welbeck with Inchbald in the late 1960s, said: "Denis was a great people person and a damned good leader – he always wanted to do better and he was very much loved by all of his clients.
"We all loved him dearly even though he always used quite a lot of words when one or two would do – he loved to chat and that was something we used to rag him about endlessly."
Inchbald edited the Cambridge graduate weekly, Varsity, and initially embarked on a career in journalism with the Daily Telegraph before moving into PR.
Brunton added that he had had a distinguished career in the Royal Navy during the Second World War.