An electric motor controller having a front face and a rear face, the front face carrying a plurality of AC output couplings and the controller carrying a converter configured to convert a received DC supply into an output AC supply for controlling an electric motor, the AC output couplings being disposed symmetrically about an axis of symmetry of the controller on the front face of the controller. Also described is an apparatus comprising: a DC series motor; and a first current supply configured to supply a first current to an armature of the DC series motor; a second current supply configured to supply a second current to a field winding of the DC series motor; and a controller configured to control the first current supply to supply the first current based on a required torque output for the motor, and to control the second current supply to supply the second current based on the first current.