Around 1964 a set of 4 submarkers (408 I to IV) were placed high above the river Garonne near the village of Fos. From 1959 onwards, Spanish foresters had tresspassed between bm408 and 409 the Ruisseau du Terme, claiming that another stream – to the north – was meant as the borderline in the 1862-treaty.
From the beginning, the border-commissioners Jean Sermet and his Spanish colleague Alija were inclined to that theory which led ultimately to the placement of the four submarkers.
The available documents (kindly provided by the Darrieu’s) tell a fascinating story. My conclusion: Sermet & Alija were wrong! Judge for yourself on this (elaborate) special page