You only have to look in Part FCL
FCL.405.A MPL — Privileges
(a) The privileges of the holder of an MPL are to act as co-pilot in an aeroplane required to be operated
with a co-pilot.
(b) The holder of an MPL may obtain the extra privileges of:
(1) the holder of a PPL(A), provided that the requirements for the PPL(A) specified in Subpart
C are met;
(2) a CPL(A), provided that the requirements specified in FCL.325.A are met.
(c) The holder of an MPL shall have the privileges of his/her IR(A) limited to aeroplanes required to be
operated with a co-pilot. The privileges of the IR(A) may be extended to single-pilot operations in
aeroplanes, provided that the licence holder has completed the training necessary to act as PIC in
single-pilot operations exercised solely by reference to instruments and passed the skill test of the
IR(A) as a single-pilot.