Found this AAIB report interesting:
Robinson R22 Beta, G-DELT
Conclusion
A helicopter has the capability of becoming airborne once its rotors are running with sufficient speed. It is important, therefore, that those at the controls at this time are suitably able to control the aircraft should it indeed start to move, for whatever reason. The CAA is currently proposing an amendment to Article 41 of the Air Navigation Order as follows:
"An operator shall not permit a helicopter rotor to be turned under power for the purpose of making a flight unless there is a person at the controls entitled to act as pilot-in-command of the helicopter in accordance with the provisions of article 21 of this order."
I read the implication to be that an Instructor could no longer ask a student to start a helicopter, with the intention that they would board prior to lift.
But what is "a person at the controls entitled to act as pilot-in-command of the helicopter in accordance with the provisions of article 21 of this order" given that at some point that same student will need to start in order to fly as a solo student?
I did skim read Article 21 which clearly makes provision for students to fly solo, but cannot see the basis for an obvious distinction between a student that would be legally allowed to start and one that was not.
Only thought is whether that student had signed the machine out (as opposed to the instructor) but couldn't see a reference to this in Article 21?
RC