[4] The document was owned by the late Luisa Isabel Álvarez de Toledo, 21st Duchess of Medina Sidonia.

[4][dubious – discuss] In 1294 Guzmán was granted tuna fishing rights by King Sancho IV of Castile in reward for his heroic defence of Tarifa.

Guzmán had been given charge of Tarifa, recently captured from the Moors, despite having fought for Alfonso X against the rebellion of his son Sancho IV.

Guzmán held Tarifa's castle against the siege of the Moors and the Infante Juan, Sancho's rebellious brother.

The ducal title of Medina Sidonia was conferred by John II in 1445 on one of his descendants, Juan Alonso de Guzmán, count of Niebla.