 The Daugleddau ports flourished in the 16th, 17th and 18th centuries, but continued to work through the 19th century by changing to using barges to tranship cargoes down river to bigger vessels at the mid-Haven ports.In the late 19th century, concerns about the potential threat posed by the French Navy prompted the construction of a number of Palmerston Forts at various strategically important coastal sites, including Milford Haven.Most of the forts are now disused.