The earliest castle here dates from the 13th century, when the site was held by the MacSweens, a powerful kindred whose lands stretched along the western seaboard. In 1262, King Alexander III granted the castle and its lands to Walter Stewart, the Earl of Menteith - a redistribution that fitted Alexander's larger project of pulling the western isles firmly into the Scottish crown's orbit. It is widely believed that Robert the Bruce landed at Lochranza in 1306 on his return from Rathlin and Ireland, on his way to claim the Scottish throne. The story is part of Arran's identity, told at every viewpoint and in every guidebook, though the documentary trail is thin. What is certain is that the loch here is one of the best natural anchorages on the west coast of Scotland - a deep, narrow inlet sheltered from almost every direction. If Bruce did land at Arran, this is where he would have done it.

The castle as it stands now is essentially a 16th-century L-plan tower house - two rectangular blocks meeting at right angles, with the entrance protected at the inner corner. The thick walls were designed for defence with firearms, not arrows, and the building has the unmistakable solidity of late medieval Scottish military architecture. In 1614 it was occupied by royal forces conducting military operations against the MacDonalds; in the 1650s, Oliver Cromwell's forces used it as a garrison during the Commonwealth's military occupation of Scotland. After the Restoration the Hamiltons, who held other estates on Arran, sold the castle to the Blackwood-Davidson family, who used it as their principal seat. By the time the building entered the modern era, it had lost its roof and most of its floors, but the shell remained largely intact - a tribute to the masons who fitted its stones together.

In 1937, the Belgian cartoonist Hergé sent Tintin to Scotland in 'The Black Island,' giving his hero a brooding castle on an island off the coast to investigate. For decades, Lochranza was identified as the model. The misunderstanding endured even after Hergé's own studio said otherwise. Charles Dierick, a researcher at Studios Hergé, has clarified that Lochranza is not the model: it has a square tower, and its silhouette is wrong. The artist Bob de Moor, who redrew the book for its colour edition, did visit Arran - but he sketched Brodick Castle, on the island's east coast. The Lochranza confusion persists nevertheless. In 2010, Channel 4 aired 'Dom Joly and the Black Island,' in which Lochranza Castle stood in for Kisimul Castle on Barra, in the Outer Hebrides - another case of one Scottish castle being used to play another, with the audience expected not to notice.

Today Lochranza Castle is in the care of Historic Environment Scotland, a scheduled monument open to visitors year-round at no charge. The interior is open to the sky; staircases lead nowhere; small chambers hold nothing but the wind and whatever weather is coming off the loch. Across the water, red deer graze on the slopes of the golf course - the village's herd is famous, and the castle ruin is one of their preferred spots. The fishing village around the castle has shrunk to perhaps two hundred people, with a single hotel, a youth hostel that began life as a Victorian hotel in 1893-94, and the Arran Distillery a short walk to the south. The castle outlasts them all and will likely outlast whatever comes next. Promontories endure. Castles, with luck, follow.