The facts of recent UK case
Marley v Rawlings (260 KB PDF) were straightforward. Mr. and Mrs. Rawlings gave instructions to their solicitor to prepare identical wills, each leaving their estate to the other, but if the other had already died, to their “adopted son, Terry Marley”. The Rawlings had two biological sons, who were effectively disinherited by these wills. Unfortunately and inadvertently, husband and wife each signed the other’s will as a consequence of the solicitor handing the wrong will to the wrong person. The mistake was discovered on the death of Mr. Rawlings, several years after the death of Mrs. Rawlings, and the Rawlings’ biological sons challenged the will.