The clause became part of contractual drafting in response to
common law rule developed by the courts known as the
rule against perpetuities. That rule provided that any future disposition of property must vest within "a life in being plus 21 years". The rule generally affects two types of transactions:
trusts and
options to acquire property. Generally speaking, such transfers must vest before the end of the maximum period, or the grant will be
void. Under the old common law, a transaction would be void even if the property
might possibly vest after the end of the maximum period, though now most jurisdictions have, by statute, adopted "wait and see" laws. In an attempt to mitigate the perceived harshness of the common law rule, and to maximise the possible length of time for which trusts in particular could subsist, lawyers began to draft so-called royal lives clauses. Royal lives were chosen because (a) it was assumed that being affluent, at least one or two members of the family could be assumed to live a reasonably long period of time, and (b) being royalty, the descendants would have reasonably ascertainable lives. In practice, a dead monarch was usually chosen so as to maximise the possibility of a grandchild or great-grandchild who would be outside of the immediate royal family having recently been born. ==Application==