A method for detecting a clutter return at a sensor, in particular in a radar system, the method comprising:- a) receiving a signal comprising a return from a first range cell and a return from a second range cell; b) filtering the return from the first range cell according to frequency to determine: a component of the return from the first range cell that is in a first frequency band and a component of the return from the first range cell that is in a second frequency band, c) filtering the return from the second range cell according to frequency to determine a component of the return from the second range cell that is in the second frequency band, d) calculating from I the magnitude of the component of the return from the first range cell that is in the second frequency band; and II the magnitude of the component of the return from the second range cell that is in the second frequency band, an estimated clutter residue in the component of the return from the first range cell that is in the first frequency band, said estimated clutter residue obtained by taking a maximum low frequency clutter value from a snapshot of proximal range cells and then offsetting by the parameter of a predetermined offset for a Doppler filter, wherein the predetermined offset scales the expected high frequency clutter according to the expected ratio of a low frequency clutter return from a background object to the high frequency clutter component of the same object. such that the estimated clutter residue in the component of the return from the first range cell that is in the first frequency band may be discarded, characterised wherein, further comprising at step d), calculating the estimated clutter residue by determining which of the components in the second frequency band has the maximum magnitude. a) receiving a signal comprising a return from a first range cell and a return from a second range cell; b) filtering the return from the first range cell according to frequency to determine: a component of the return from the first range cell that is in a first frequency band and a component of the return from the first range cell that is in a second frequency band, a component of the return from the first range cell that is in a first frequency band and a component of the return from the first range cell that is in a second frequency band, c) filtering the return from the second range cell according to frequency to determine a component of the return from the second range cell that is in the second frequency band, d) calculating from I the magnitude of the component of the return from the first range cell that is in the second frequency band; and II the magnitude of the component of the return from the second range cell that is in the second frequency band, an estimated clutter residue in the component of the return from the first range cell that is in the first frequency band, said estimated clutter residue obtained by taking a maximum low frequency clutter value from a snapshot of proximal range cells and then offsetting by the parameter of a predetermined offset for a Doppler filter, wherein the predetermined offset scales the expected high frequency clutter according to the expected ratio of a low frequency clutter return from a background object to the high frequency clutter component of the same object. such that the estimated clutter residue in the component of the return from the first range cell that is in the first frequency band may be discarded, characterised wherein, further comprising at step d), calculating the estimated clutter residue by determining which of the components in the second frequency band has the maximum magnitude. I the magnitude of the component of the return from the first range cell that is in the second frequency band; and II the magnitude of the component of the return from the second range cell that is in the second frequency band,