A Few Questions?

Here is an image of a class of communicators. What was the class? When was the class held?, Who are the students? Who was the Instructor? Who are the officers? and where was the image taken?

L – R Standing – Tel Clem Mellish, Tel Bob Hutchins, ?, Tel Ron Tapuke, Tel Maurice Garvie.

L-R Sitting – CPO Tel Bill Holohan, Lt Arty Hay, Lt Cdr Egbert Biggs, Yeoman Jock McNeil