4.—(1) No offence is committed under section 23 of the Hazardous Substances Act before 1st April 2010 and no hazardous substances contravention notice may be issued before that date in relation to a hazardous substance which is on, over or under any land, if—
(a)the substance was present on, over or under the land at any time within the period of 12 months ending on 1st October 2009 and was not a substance or quantity of substance for which hazardous substances consent was required before that date; and
(b)the substance is not present during the period beginning on 1st October 2009 and ending on 31st March 2010 in a quantity greater in aggregate than the established quantity.
(2) In paragraph (1) “the established quantity”, in relation to any land, means the maximum quantity which was present on, over or under the land at any one time within the period of 12 months ending on 1st October 2009.