1. A method of tracking a non-rigid object in a plurality of images including: generating a first set of parameters for a parameterised shape model by matching a first set of land-mark points to points in a first image of the plurality of images, wherein the first set of land-mark points is fitted to an object in the first image according to one or more constraints defined independently of the object; and generating a second set of parameters for the parameterised shape model by matching a second set of land-mark points to points in a second image of the plurality of images, wherein the second set of land-mark points is fitted to the object in the second image according to: the one or more constraints defined independently of the object; and the first set of parameters, wherein the first and second sets of parameters define a tracking of the non-rigid object between the first and second images.