4.—(1) Subject to sub-paragraph (2) weights on plates first affixed to a vehicle on or after 31st December 1976 shall be shown in kilograms, and weights on plates first so affixed before that date may be shown in—
(i)kilograms; or
(ii)tons and decimals thereof together with the equivalent weight in kilograms; or
(iii)tons and decimals thereof.
(2) Where a new weight is first shown on a plate by virtue of paragraph 2(2) the weight shall be shown as if it was on a plate first affixed to a vehicle on the date it was first shown.