through the valleys of the Nyfer and Gwaun, then south along the course of the Western Cleddau. Historically, the tidal estuary enabled sea traffic to reach Haverfordwest. It was important also for the export of anthracite, which was mined on its west bank and shipped from Hook. Daugleddau Estuary and Milford Haven The combined estuary – the Daugleddau - from Picton Point to the Blockhouses guarding the harbour entrance, is a massive ria which is deep and wide, but sufficiently serpentine to be sheltered from high winds and rough seas, and is thus an excellent natural harbour. Because it can easily accommodate supertankers of 300,000 tonnes and more, it became from 1957 an important centre of the oil industry, with Esso, BP, Texaco, Gulf Oil and Amoco operating terminals and oil refineries. In the mid-1970s, it became briefly the UK’s second biggest port in terms of tonnage. The Daugleddau and its several tributary tidal reaches are known collectively as Milford Haven. Length (from Picton Point to the Blockhouses) about 27 km. Historically, the estuary gave seaborne access to castles such as Pembroke and Carew, allowing these to be used as depots in the Norman invasion of Ireland. It was important in the early Industrial Revolution, shipping anthracite from Llangwm, Landshipping and Crescelly, and limestone from Lawrenny and West Williamston. A small fishing industry operated from harbours such as Pill, Angle and Dale, but in 1790 the building of the new town of Milford commenced, and a large herring fishery grew up based on its docks. In its heyday, it became the UK’s seventh largest fishing port, operating several hundred fishing trawlers, but with exhaustion of inshore fishing grounds, the docks were too small for large ocean-going trawlers, and fishing is now virtually totally non-existent. Milford was originally built for a naval dockyard, but this project was transferred in 1814 to Pembroke Dock on the opposite side of the estuary, where it operated until closure in 1926. The town of Neyland, originally known as New Milford, was also purpose-built, this time by the Great Western Railway as a transatlantic shipping terminal. Its functions were largely transferred to Fishguard in the early 20th century. Ecology Both branches of the Cleddau are noteworthy for their diverse aquatic ecology that has been largely untouched by man's activities. The rivers support otter populations and a wide variety of fish species including Lampreys. Stretches of both