Under the Will of Mary’s father, John Williams of Halton in the Parish of Chirk, Denbighsire, proved in 1705, she was, while she was still a minor, appointed as his sole Executrix, despite having another brother and sisters. During her minority this duty was carried out for her by Peter Foulkes and Thomas Cupper as the grant of probate and a document in Chirk Castle Records of Sept 10 1710 shows. John Williams Will is held in the National Library of Wales although damaged.

Mary’s marriage settlement with Richard Jones is held in the Pen y Lan MSS at Denbighshire Record Office. She is described as the daughter of John Williams of Halton, Denbighshire. The trustees of the settlement are the same “Peter Foulkes of Cadwgan” (nr Wrexham) and “Thomas Cupper of Llantysilio.” Mary is described as “of Cadwgan” so it is likely that after her father’s death Peter Foulkes became her legal guardian.

Thomas Cupper’s daughter inherited Lantysilio Hall from her father. She married Thomas Jones Senior and it passed down to Thomas Jones Jnr of Llantysilio himself one of the trustees of Ruth Speed’s Will later in the century.

Mary’s will was proved in 1765 and contains bequests to her brother in law Thomas Jones, her husband’s nieces Magdalene and Ellin and her daughters Ruth and Mary.