1. A method of processing graphics primitives for a frame to be displayed, the method comprising steps of: allocating each primitive to at least one of a plurality of tiles forming the frame to be displayed; for each tile, storing in a primitive memory a primitive list identifying vertex data for vertices of the primitives allocated to the corresponding tile; and performing tile processing separately for each tile, the tile processing comprising: (i) reading the primitive list for the tile from the primitive memory; (ii) if the primitive list identifies a target primitive that satisfies a clipping condition, performing a clipping operation for clipping the target primitive with respect to the clipping boundary to generate additional vertex data for at least one additional vertex for a clipped primitive not identified in the primitive list, the clipped primitive extending beyond the clipping boundary by a smaller amount than the target primitive; (iii) performing at least one further graphics processing operation using the vertex data identified in the primitive list and the additional vertex data generated by the clipping operation; and (iv) outputting display data generated by the at least one further graphics processing operation for the tile.