In 2003, three years after the mutual wills were executed, Robert died.
The mutual wills unambiguously divided any remaining estate among the four children after both Robert and Dorothy's death, and it was specifically irrevocable.
The principal part of the litigation focused on the right of Camilla Ranc, who survived her husband, to leave her property contrary to the mutual will.
35) An example of this was through the making of a mutual will as a consensual instrument.
Although counsel in Dufour cited some authority in support of the proposition that where two people had made a mutual will either of them might revoke secretly, (38) Lord Camden rejected such authority, saying that:
First, how far the mutual will shall operate as a binding engagement, independent of any confirmation by accepting the legacy under it.
In the common law, this left hanging the question of the implications of this 'common fund', both for the survivor and the intended beneficiaries of the agreed succession plan reflected in the mutual will.
225) The Court held the will to be a mutual will simply on the basis of its terms (which conferred only a life interest to the surviving testator).
112) For example, where one testator revokes the mutual will in his or her lifetime, failing to leave the other an agreed interest in the property: Bigg  2 Qd R 11, 15 (McPherson J).
It has been more than 200 years since the leading case on mutual wills was handed down in Dufour v Pereira.
Even in respect of key issues, such as whether mutual wills are based in equity or contract law, the Court of Appeal's view is unclear.
These cases show it is important to understand the difference between Mirror Wills (which can be changed) and Mutual Wills