Laugharne Corporation is, with the City of London Corporation, one of the last two surviving medieval corporations in the United Kingdom. It was established in 1291 by Sir Guy de Brian, a Marcher Lord whose name is still toasted at the annual Portreeve's feast. The portreeve, sworn in each year on the first Monday after Michaelmas, wears a chain of gold cockle shells - one added by each new holder, his name engraved on the reverse. Seventy-six senior burgesses still hold strips of common land on a hill called The Hugdon, farmed in a form of medieval strip-cultivation that elsewhere in Britain vanished with the enclosures. Court leet, court baron, big court, little court - the language of medieval governance has been quietly continued here for more than seven centuries while Norman castles fell, kingdoms rose, and the rest of Wales modernised.

Beneath the medieval town runs a much older story. Just southeast of Laugharne, a limestone bluff called Coygan once stood above a coastal plain now drowned by the Bristol Channel. A cave on its face was excavated five times between 1865 and 1965, and what came out kept pushing the dates further back: flint tools, animal bones, the discarded gear of hunters who sheltered here over 50,000 years ago. By the late Bronze Age there was a permanent settlement on the bluff; by the Iron Age, a defended promontory fort; by Roman times, a high-status native settlement rich enough to leave behind a hoard of more than 2,000 coins, found later at Island House, and imported finewares that archaeologists describe as one of the richest assemblages from any native settlement in southwest Wales. Laugharne may be the oldest continuously inhabited place in Wales.

Laugharne Castle rises directly out of the estuary mud, its sandstone walls reflecting in the salt water at high tide. The Normans built the first version - originally called Abercorran Castle - around 1116, when Henry I ordered the land fortified against the returning Welsh heir Gruffydd ap Rhys. It changed hands repeatedly through the centuries, was lavishly converted into a Tudor mansion by Sir John Perrot, then ruined in the Civil War. In 1644, Parliamentary forces under Major-General Rowland Laugharne - a member of the family that had given the town its English name - laid siege to the castle his own ancestors had once held. The bombardment shattered the gatehouse and spread collateral damage across neighbouring Island House. The castle has been a roofless ruin ever since, which is precisely how Turner painted it and how Dylan Thomas saw it from his writing shed on the cliff above.

Thomas moved into the Boat House in May 1949, with his wife Caitlin and their children, brought there by his friend the novelist Richard Hughes who lived in Castle House. The house clings to a sea wall under the cliff, with herons stalking the mudflats at the bottom of the garden. Above it, in a converted garage perched at the cliff edge - the famous writing shed - Thomas worked on the play he was calling Llareggub: A Piece for Radio Perhaps, eventually broadcast and published as Under Milk Wood. Across the town at Brown's Hotel on King Street, he drank. The hotel was practically his second study, the pub regulars his eavesdropping material. He died in New York in November 1953, age 39, days after collapsing at the Chelsea Hotel. They brought his body home. He is buried in the churchyard of St Martin's, his grave marked by a plain white wooden cross.

The cockle women of Laugharne and neighbouring Llansaint once harvested 650 tons a year from the estuary beds, working the mud with rakes and donkeys. The Taf and Towy estuaries here have one of the largest tidal ranges in the world, exposing miles of glittering flats at low water and then re-flooding the channels so quickly that the old saying held you could outrun a horse on the way out but not on the way back. The cockle trade is intermittent now, the donkeys gone, the channels silted to where the medieval Gosport Harbour once anchored 350-ton vessels and now barely floats a yacht. But the estuary still does what an estuary does: shifts, shines, hosts curlews and oystercatchers, and lays down at twilight the kind of slow violet light that explains why a poet would settle here and never leave.