In the late sixth century, Rhydderch son of Tudwal ruled here as a Christian king of Alt Clut, fighting the pagan Angles of Northumbria and acting as patron to Saint Kentigern, the apostle of Strathclyde and founder of the bishopric of Glasgow. For more than two centuries from the mid-seventh, Dumbarton was the centre of Brittonic power in northern Britain, the only surviving Celtic British kingdom outside Wales. Then in 870, the Viking leaders Amlaíb and Ímar besieged the rock for four months until the well ran dry, sacked the fortress, and took prisoners back to Dublin. The kingdom did not end - it relocated upriver to Govan and became known as Strathclyde - but Dumbarton's eight-hundred-year run as a Brittonic capital was over. The rock waited for its next role.

Dumbarton Castle - perched on top of the rock like a stone hat - has an inventory of visitors that reads like a Scottish history curriculum. The fortress was royal long before the town was a burgh. Its ownership shifted from Scottish to English to Scottish again during the Wars of Independence. William Wallace was imprisoned here for a short time after his capture by the English. In Levengrove Park at the foot of the castle, a grave-site marks the resting place of the viscera of Robert the Bruce - in an era when long-distance funeral journeys made it practical to bury a king in pieces, his organs were left here while his body went on to Dunfermline Abbey. The Old Dumbarton Bridge across the Leven, with its five segmental arches, was built in 1765 by John Brown of Dumbarton at the urging of the Duke of Argyll, who wanted easier access to Glasgow from his estate at Rosneath.

From the mid-eighteenth to the early nineteenth century, Dumbarton's main industry was glassmaking. As glass declined, shipbuilding took its place and dominated the town well into the twentieth century. The most famous ship built here is probably the Cutty Sark, launched in 1869 by Scott and Linton - one of the last tea clippers ever constructed, and one of the fastest. She survives in dry dock at Greenwich, the last of her type. The greatest local yard was William Denny and Brothers, which closed in 1963. Denny's was a remarkably innovative firm: they pioneered high-pressure marine turbines, built one of the world's first commercial ship model testing tanks (the Denny tank still exists as part of the Scottish Maritime Museum, a basin as long as a football pitch with original Victorian machinery), constructed an early helicopter in 1909, and in their final years even developed a hovercraft, the Denny D2 Hoverbus.

When shipbuilding faded, whisky took over. In 1936 the Canadian distilling firm Hiram Walker bought the Glasgow-based Ballantine's, and in 1938 they built a vast grain whisky distillery on the Leven, on the site of the old Archibald McMillan shipyard. At its peak, the Dumbarton distillery was the largest grain distillery in Europe, the red-brick complex dominating the town's skyline for over sixty years. After Pernod Ricard's 2005 acquisition of Allied Domecq, the mothballed buildings were earmarked for demolition; the last of them came down in January and February 2017. The site is now housing. The tower is gone. The skyline, for everyone who grew up here, has the wrong shape now.

Sir Jackie Stewart - three-time Formula 1 World Drivers' Champion between 1969 and 1973 - was born here. His family ran the garage at Dumbuck in Milton, east of the town. The new wave musician David Byrne, founding member and principal songwriter of Talking Heads, was also born here before emigrating with his family to North America. Robert Burns was made a freeman of Dumbarton; in a letter dated 7 July 1787 he described running a drunken race on the banks of Loch Lomond with a wild Highlandman, and getting bruised badly enough that he postponed his Edinburgh journey by four weeks. The town is immortalised in 'Dumbarton's Drums', a traditional song with verses still sung in local pubs. Prince Harry and Meghan Markle became Earl and Countess of Dumbarton upon their marriage in 2018, a title largely ornamental but inherited from the place all the same. The rock has outlasted every kingdom that ever sat on it, and it is good at outlasting things.