Looked into this the other day. . .
Only an instructor can fly P1 from the left seat and only as part of a 'training flight' from licenced airfield to licenced airfield.
Any other flights, including and especially 'corporate flying' (eg. pax owns machine) P1 must be flown from the right seat.
It is possible to fly solo from left seat in a 22 & 44 but it's not legal.