Supervision
Refer; ANO Schedule 8, Part B
[para-phrased]
An AFI (I presume the old UK/AFI) may only instruct when an FI is present at the aerodrome of departure at the time the flying lesson commences and at the place of landing when the flying lesson ends. Nothing about intermediate landings that may take place as part of the lesson.
An FI(R) has no such restriction applied to them, therefore an FI is not required to be present. An FI(R) appears only to be restricted to the first solo bits! No telephone required eigther.