19.—(1) Subject to sub-paragraph (2), the Agency shall not agree a variation which permits any act or omission a proposal for which would, had it been made in the application for a licence, have caused the Agency to refuse to grant the licence under paragraph 2 of Part 1.
(2) For the purposes of sub-paragraph (1), the Agency, in considering whether to vary a licence, shall treat all scientific knowledge which it has at that time as if it had had it at the time it granted the licence.