It is legally possible for couples to make mutual wills by which each binds the other not to alter their bequests at any point in the future, save by mutual agreement. As a High Court ruling showed, however, the inherent inflexibility of such arrangements is one good reason why lawyers usually advise against them.

A married couple made mutual wills by which they each bequeathed their estates to the other. The wills provided that, on the death of the second spouse, the entirety of his or her estate would pass to their third-eldest child. Following the husband's death, however, the wife made a fresh will by which she appointed their sixth-eldest child as her sole beneficiary.

The effect of the mutual wills, if valid, was that, in the absence of their agreement to the contrary, each spouse bound the other to bequeath his or her estate to the third child. When the death of the husband rendered any such agreement impossible, the obligation on the wife to do so became irrevocable.

The sixth child sought a formal declaration that his mother's final will was valid. In resisting his claim, however, the third child asserted that the document was of no effect in that it conflicted with the terms of the earlier mutual wills.

Ruling on the matter, the Court noted that it is notorious to lawyers practising in the field that a decision to make mutual wills needs to be considered with the greatest care. The inflexibility of such arrangements, which take no account of any future changes in circumstances, usually renders them inappropriate.

The couple understood the effect of their agreement to enter into mutual wills. It was, however, certainly a transaction that called for an explanation. In setting aside the agreement, the Court was not satisfied that they had entered into it free from the third child's undue influence. The ruling meant that the mother's final will took full effect and that the sixth child, not the third, was the beneficiary of her estate.