| Joseph Percival William Mallalieu | October 1964 | February 1966 |
| Dr David Anthony Llewellyn Owen | 3 July 1968 | 18 June 1970 |
| Peter Michael Kirk | June 1970 | November 1972 |
| Philip Antony Fyson Buck | 1972 | 1974 |
| Frank Ashcroft Judd | March 1974 | April 1976 |
| Albert Edward Patrick Duffy | 1976 | May 1979 |
| Herbert Keith Speed | May 1979 | 18 May 1981 |