Montreuil was a thriving port before the river silted up in the 1300s (the sea is now about 25 km away).
The river silted up in the 12th century.
mnli hypothesis: The river silted up in the 12th century. premise: Montreuil was a thriving port before the river silted up in the 1300s (the sea is now about 25 km away).