An axial flux permanent magnet machine comprising: a pair of axially spaced first components; a second component positioned axially between and equidistant from the first components; and a translation mechanism coupled to each of the first components, the translation mechanism being configured to translate the first components axially away from the second component; wherein either the pair of first components or the second component is arranged to rotate about a shaft, characterized in that either the pair of first components or the second component comprises two radially spaced annular arrays (56, 58) of permanent magnets (40, 60), the second annular array is radially inside the first annular array, wherein the number of poles of the first annular array is equal to the number of poles of the second annular array, wherein magnets of each annular array have poles alternately arranged in a N-S-N-S sequence around the arrays; and a retaining arrangement, the retaining arrangement comprising a retractable pin or a retractable key configured in a first configuration to retain the magnet arrays (56, 58) in like-pole alignment, where the permanent magnets of the second array are arranged so that like poles are radially aligned with the permanent magnets of the first array, and in a second configuration to release the magnet arrays (56, 58) to rotate to opposite-pole alignment where the permanent magnets of the second array are arranged so that opposing poles are radially aligned with the permanent magnets of the first array, and either the pair of first components comprises a pair of rotors and the second component comprises a stator, or the pair of first components comprises a pair of stators and the second component comprises a rotor. a pair of axially spaced first components; a second component positioned axially between and equidistant from the first components; and a translation mechanism coupled to each of the first components, the translation mechanism being configured to translate the first components axially away from the second component; wherein either the pair of first components or the second component is arranged to rotate about a shaft, characterized in that either the pair of first components or the second component comprises two radially spaced annular arrays (56, 58) of permanent magnets (40, 60), the second annular array is radially inside the first annular array, wherein the number of poles of the first annular array is equal to the number of poles of the second annular array, wherein magnets of each annular array have poles alternately arranged in a N-S-N-S sequence around the arrays; and a retaining arrangement, the retaining arrangement comprising a retractable pin or a retractable key configured in a first configuration to retain the magnet arrays (56, 58) in like-pole alignment, where the permanent magnets of the second array are arranged so that like poles are radially aligned with the permanent magnets of the first array, and in a second configuration to release the magnet arrays (56, 58) to rotate to opposite-pole alignment where the permanent magnets of the second array are arranged so that opposing poles are radially aligned with the permanent magnets of the first array, and either the pair of first components comprises a pair of rotors and the second component comprises a stator, or the pair of first components comprises a pair of stators and the second component comprises a rotor.