Where a disposition is limited by reference to the time of death of the survivor of a person in being at the commencement of the perpetuity period and any spouse[F1 or civil partner]F1 of that person, and that time has not arrived at the end of the perpetuity period, the disposition shall be treated for all purposes, where to do so would save it from being void for remoteness, as if it had instead been limited by reference to the time immediately before the end of that period.