1. A method of classifying a behaviour of a detected object in a video frame, said video frame comprising a plurality of blocks and said detected object being associated with a subset of said plurality of blocks and a set of parameters, said method comprising the steps of: (a) associating a behaviour model with each of said plurality of blocks, wherein each behaviour model includes a set of behaviour modes; (b) for each block in said video frame associated with the detected object: (i) determining a set of behaviour statistics associated with the detected object, based on said detected object and said set of parameters; and (ii) comparing the determined set of behaviour statistics with each behaviour mode in the set of behaviour modes associated with that block to determine an abnormality measure associated with said block; and is (c) classifying the behaviour of the detected object based on the abnormality measures associated with the subset of said plurality of blocks associated with said detected object.