An actuator arrangement for an electromagnetically operated fuel injector includes a generally cylindrical actuator core having a longitudinal axis and defining an inner pole face of the actuator arrangement. The actuator core is formed of a bespoke magnetic material. A wire coil is disposed around the actuator core arranged to be connected to a power source to generate a magnetic field around the coil. A pole member is formed of a high strength material and defines an aperture for receiving the actuator core. The pole member defines an outer pole face of the actuator arrangement substantially co-planar with the inner pole face. An armature is movable in a direction parallel to the longitudinal axis in response to the magnetic field. The magnetic field passes into the armature in the region of the inner pole face and into the armature in the region of the outer pole face.