This 'difficulty' has been in the rules since the 90 day requirement was introduced. There are any number of postings on here and Flyer spelling out the CAA interpretation which was given to the AAIB.
But I'm left in the same situation as dublinpilot. If it is legal to let a passenger fly the aircraft, then where is the regulation which says someone flying the aircraft is not the sole manipulator of the controls - if the PIC does not manipulate the controls?
'Cos from the comonsense point of view (I know the last thing one would expect is common sense in aviation regulation but,) if I do not manipulate the controls - then someone else must be doing it! If they are the sole manipulator of the controls, then that is what they are.
I too feel that the lack of a proper regulation quote suggests this is what they want it to say rather than what it actually says....
And again, long before the 90 day requirements most groups had these sort of sensible arrangements to try and ensure currency.