1. A method of tracking a target imaged in video footage, the method comprising the steps of: (i) identifying the target to be tracked in a first image frame, the target being located at a first position; (ii) defining a first template area around the first position; (iii) generating a first population of sub-templates by sampling from the first template area; (iv) searching for an instance of each of the first population of sub-templates in a second image frame, and determining the location of each instance in the second image frame; (v) determining a second position of the target in the second image frame in dependence on the locations of the instances; (vi) selecting a selection of the first population of sub-templates in dependence on the locations of the instances of each of the sub-templates in the second frame; (vii) defining a second template area defined around the second position; (viii) generating a second population of sub-templates comprising the selection of the first population of sub-templates, and a set of new sub-templates generated by sampling from the second template area; and (ix) iterating steps (iv) to (viii) above in respect of further image frames, using the second population of sub-templates and the second position from a preceding iteration in place of the first population of sub-templates and the first position, thereby determining a series of target positions, and inferring the target track therefrom, wherein the step of identifying a second position of the target comprises the step of determining a permitted area, and constraining the second position to lie within the permitted area, and wherein the step of searching for an instance of each of the first population of sub-templates in a second image frame includes searching areas of the second image frame outside the permitted area.