§ 11. "That during a period of five years beginning on the nineteenth day of April, nineteen hundred and twenty-seven, there shall be charged on the importation into Great Britain or Northern Ireland of articles of translucent pottery or of vitrified pottery, being either articles suitable for use in connection with the serving of food or drink or component parts of such articles, a duty of Customs at the rate of one pound and eight shillings for every hundredweight thereof."