An electric power assisted steering system for a vehicle, comprising: a steering mechanism which operatively connects a steering wheel to road wheels of the vehicle, a torque sensor arranged to, in use, produce a torque signal indicative of the torque carried by a portion of the steering mechanism, an electric motor operatively connected to the steering mechanism, a signal processing unit arranged to, in use, produce from the torque signal a torque demand signal representative of a torque to be applied to the steering mechanism by the motor, the signal processing unit comprising a first calculating unit arranged to calculate an initial torque demand signal dependent on the torque signal, and a second calculating unit arranged to, in use, calculate a torque damping signal indicative of an amount the initial torque signal is to be damped in order to generate the torque demand signal, and a motor drive stage arranged to provide, in use, a drive current to the motor responsive to the torque demand signal, in which the second calculating unit comprises an input for a signal dependent upon the torque demand signal, a differentiator, arranged to, in use, differentiate the input signal dependent upon the torque signal and a high pass filter arranged to filter the input signal to reduce low frequency components thereof.