The Daily Express of Friday 4 June 1971, page 16, had an item as follows:
The Baron
Police Constable Charles Muff, aged 24, will be on duty in Bradford, Yorks, today as the third Baron Calverley, following his father's death.
That suggests that his father died on 3 rather than 4 June. The 3rd Baron is Charles Rodney, but I believe (pace the Daily Express) that he is known as Rodney.