1. A method of recognising a moving feature in a video sequence, said moving feature having a characteristic pattern over said video sequence, said video sequence comprising a first frame and a plurality of following frames, said method comprising identifying points of interest in each frame of said video sequence; determining, for each frame other than said first frame, at least one point of interest that corresponds to a point of interest in the preceding frame in said video sequence; constructing a plurality of trajectories for a point of interest in said first frame, each trajectory comprising a location in said first frame and at least one of said following frames of said video sequence, said location in said first frame being the location of said point of interest in said first frame, said location in said at least one following frame being determined by sequentially considering each following frame of said sequence where at least one trajectory extends to the preceding frame and including in that trajectory the location of the point of interest that corresponds to a point of interest in the preceding frame included in the trajectory; and comparing said plurality of trajectories with said characteristic pattern.