| Richard William Marsh | 1965 | 1966 |
| Peter David Shore | April 1966 | January 1967 |
| Edmund Emanuel Dell | April 1966 | August 1967 |
| Dr Jeremy William Bray | 1967 | 1969 |
| Gerald Teasdale Fowler | September 1967 | October 1969 |
| Neil George Carmichael | October 1969 | June 1970 |
| David Ernest Campbell Price | April 1970 | October 1970 |