Actor and presenter Les Dennis was among those paying tribute.
The former Family Fortunes host, 67, wrote on Twitter: “So sad to hear the wonderful actor Ronald Pickup has died. Saw him in Waiting for (Godot). He was magnificent. He came and guested on Coronation Street. He was so down to earth. I was in awe. RIP.”
The National Theatre’s official Twitter account said: “We’re very sad to hear that Ronald Pickup has died.
“Ronald was an exceptional actor and had a long history with the NT, starting with 1964’s The Royal Hunt of the Sun.
“He went on to feature in 36 of our productions, and was a regular at The Old Vic under Laurence Olivier.”