Abstract: An axial flux rotating electrical machine is disclosed, which comprises a stator sandwiched between two rotors. The machine comprises retention means for retaining magnets on the rotor, the retention means comprising a back plate with a plurality of protrusions which define a plurality of pockets for accommodating the magnets. The retention means is arranged such that the magnets can be inserted into the pockets and held therein, and the retention means with inserted magnets can be fixed to a rotor so as to retain the magnets axially and tangentially. A cooling jacket for the stator, and techniques for securing the stator to the machine, are also disclosed.