I was going to leave Madeleine alone for a bit, but while I was researching the marriage of my great-great-great grandfather several things about Madeleine and Emile’s relationship clicked into place.
In her letters to Emile, Madeleine signed herself as ‘your wife’ and addressed him as ‘husband’. Given that Madeleine had also had a sexual relationship with Emile, and moreover had written about it, it could have been argued in a court of law that in fact they were married as the law stood in Scotland at the time.
This isn’t an isolated case, the Yelverton case a few years later turned on a similar point.
There are also cases of people in similar irregular relationships being made to formalise the relationship.
Therefore, if Madeleine was to marry Walter Minnoch, as her father desired, she had to destroy any proof that there was of the nature of the relationship with Emile, which is why she wanted her letters back.
As long as he had her letters, Emile L’Angelier had a hold over her and could potentially blackmail her.
Poisoning Emile when he would not return her letters made the problem go away, or so she thought …