§ 18. "That there shall be charged on legacies derived from a testator or intestate dying on or after the sixteenth day of April, nineteen hundred and forty-seven, and successions arising on or after that day, on which legacy or succession duty is payable or has before that day been paid under the enactments now in force, a further legacy or succession duty at a rate equal to the rate of aggregate rate of the duty thereon under those enactments; and this Resolution shall apply also to other legacies and successions so as to authorise charging the further legacy or succession duty thereon on deaths and other events happening on or after the said sixteenth day of April."