For the purposes of the references to a thousand cigarettes in paragraph 1 in the Table in Schedule 1 to this Act . . . F1 any cigarette more F4than 8 cm. long (excluding any filter or mouthpiece) shall be treated as if F3the first 8 cm. of it, each 3 cm. portion of the remainder of it (if any) and the remaining portion of it (if any) were a separate cigarette.