The name has nothing to do with the river. Despite the obvious link to nearby Otterton and Yealmpton, Plympton was never sited on the Plym. It stands on the Ridgeway, the ancient trackway running down from Dartmoor, and its oldest written form, Plymentun, appears in an Anglo-Saxon charter dated to around 900 AD. The likely Old English root is plymen, meaning growing with plum-trees. Plympton was, in essence, the plum-tree farm above the moor. Only later, in the early thirteenth century, did somebody look at the town and its neighbour Plymstock and back-form a name for the river running between them. The river borrowed its name from the town. The town never borrowed anything from the river.

Walk down Fore Street today and you can still read the medieval town in the kink of the lanes and the green slate cottages with their granite quoins. Plympton was a stannary town, an officially recognised centre for the smelting and stamping of Dartmoor tin, and a feudal capital under the Norman barony of Plympton. Richard de Redvers, a trusted supporter of Henry I, was granted the barony around 1100 and built the motte-and-bailey castle whose grassy mound still rises above the rooftops. The de Redvers became Earls of Devon. Their lands and titles eventually passed to the Courtenay family, feudal barons of Okehampton, and the castle settled into ruin. The Domesday Book of 1086 recorded Plympton in the king's own hands, with 27 villagers, 12 smallholders, and 6 enslaved labourers - the latter a reminder that medieval Devon was built on more than free hands.

In 1723, in a stone house on the Ridgeway, a boy was born whose paintings would come to define how Georgian England looked at itself. His name was Joshua Reynolds, and his father was headmaster of Plympton Grammar School, a building still standing in the centre of town. Reynolds went on to become the first president of the Royal Academy of Arts, and in 1773, at the height of his fame, he served as mayor of his home town. Two other notable pupils followed him through the grammar school: Benjamin Haydon, the ambitious historical painter who spent much of his life in debt and died in 1846, and Charles Lock Eastlake, who became first Director of the National Gallery and first president of the Royal Photographic Society. Reynolds painted his friends the Parkers at nearby Saltram House so often that many of those portraits still hang there, looking down at visitors with the same composed, slightly amused expressions Reynolds gave half of Georgian society.

Before the Reform Act of 1832 swept it away, Plympton was one of England's most notorious rotten boroughs - a tiny constituency sending two MPs to Westminster on the strength of a handful of voters. The seats had a habit of attracting men of consequence rather than men of Plympton. Sir Edwin Sandys, who helped found the Jamestown colony in Virginia, sat for Plympton. So did Richard Strode, whose imprisonment for speaking out against tin miners' grievances led, in 1512, to legislation establishing Parliamentary privilege - the principle that MPs cannot be punished for what they say in the House. A modest Devon stannary town, almost by accident, helped shape the freedoms of every parliament that followed.

Plympton today has 68 listed buildings, more than many full-sized English towns. The Grade I-listed Plympton House sits at one end of Fore Street; the Grade II*-listed Old Rectory, Guildhall, and Tudor Lodge punctuate the streetscape. Two churches anchor the parish: the Norman Church of St Maurice, and St Mary's, dedicated in 1311 as a chapel attached to the great Plympton Priory - once the second-richest monastic house in Devon, now mostly vanished apart from its gatehouse. Each midsummer, the Lamb Feast spreads across Castle Green beneath the old motte, a fete the Civic Association has been organising for generations. The trains roar straight through Plympton on the main London line without stopping; the town is one of the few in Britain of its size to lack its own station, a quiet final indignity from the river it once gave a name to.