This name is Norse, and Lochlainn was the name of the senior branch in Tirconnell of the Ui’neill descendants of the pagan King Niall of the Nine Hostages. Until 1241 the MacLochlainns were virtual rulers of Ulster, until they suffered defeat at the hands of King Brian O’Neill. Their chief, Donall MacLochlainn, was killed in the battle, along with most of his immediate kin. The name appeared in Scotland by the thirteenth century, when Lachlan Mor lived on the shores of Loch Fyne. Lachlan was a great warrior and a descendant of the Irish kings.

In 1292, Archibald Maclachlan was one of the twelve barons whose lands were formed into the sheriffdom of Argyll. Ewen Maclachlan appears on the Ragman Roll as a noble of Scotland, swearing fealty to Edward I of England in 1296. Gillespie, probably the son of the chief, supported Robert the Bruce and attended his first Parliament at St Andrews in 1308. He is also recorded in a charter of 1314, where he granted a stipend to the friars at Glasgow from his lands of Kilbride. By the early fifteenth century the chiefs were described as ‘Lords of Strathlachlan’. In 1436, Iain, Lord of Strathlachlan, granted a charter to his cousin, Alan, creating him seneschal of the lands of Glassary in Argyll. Donald Maclachlan confirmed a grant to Paisley Abbey of an annual payment, again from the lands of Kilbride. The Maclachlans recognised the rising power of the Campbells in Argyll, and allied themselves to the earls. Iain Maclachlan witnessed a bond by Stewart of Appin in favour of the first Earl of Argyll in 1485. His son, Archibald, married a daughter of the chief of the Lamonts. From this marriage came Lachlan Maclachlan who, as part of the Earl of Argyll’s suite, travelled to France for the marriage of James V. The king’s wedding, to the eldest daughter of Francis I of France, was held in Paris.

In 1615, the Maclachlan chief, Lachlan Og, led his clan in Argyll’s foray against the Macdonalds of Islay. He had previously obtained a charter to his lands from James VI in 1591, but in 1633 he procured an Act of Parliament confirming him as Laird of Maclachlin. His lands, which were enumerated in the Act, extended to over thirty-four farms in Strathlachlan and Loch Fyne. The civil war allowed many clans an opportunity to settle old scores, and the Maclachlans fought with their neighbours, the Lamonts. Lachlan Maclachlan of that Ilk accepted a commission in 1656 from Oliver Cromwell, the Lord Protector, to be justice of the peace for Argyllshire. His son, Archibald, the fifteenth chief, received a charter in 1680, erecting his whole lands into the Barony of Strathlachlan with Castle Lachlan as its seat. He died in 1687 shortly before his clan embarked upon the first of the Jacobite campaigns.

The Maclachlans fought for Viscount Dundee at Killiecrankie in 1689, and the Maclachlan chief himself was present at the raising of the standard of James VIII, the ‘Old Pretender’, in Scotland in 1715. The Maclachlans followed the Earl of Mar to the Battle of Sheriffmuir. It is said that the chief was harried by the Campbells until his death in 1719, for his part in the rising. In 1745 the Maclachlans rallied to Prince Charles Edward Stuart, making their way through Campbell country in time to join the prince at Prestonpans. The chief was appointed to the prince’s staff as commissary-general. When the Jacobite army invaded England, it was Maclachlan who was sent north to Perth to summon reinforcements. His strongest entreaties for haste were of no avail, and fresh troops idled at Perth while the tide of fortune turned against the prince. The retreat from Derby did not dismay the Maclachlan, who led three hundred of his clansmen to Culloden. He was riding to order the Highland advance when he was killed by a stray cannon shot. The Maclachlan colours were burned on the Duke of Cumberland’s orders by the public hangman at Edinburgh. Castle Lachlan was left in ruins and the chief’s family was forced to flee. Lachlan was declared forfeit for treason, but as the estates had been conveyed to his son over a decade before the rising, they escaped untouched. A new mansion house was built in the nineteenth century in sight of the ruins of the ancient castle.

During the Second World War, the chiefship was assumed by the late Marjory Maclachlan of Maclachlan, the twenty-fourth chief. Her father, Major John Maclachlan, had commanded the Argyllshire Volunteer Regiment during the First World War. He was Vice Lord Lieutenant of Argyll and a member of the Royal Company of Archers (the monarch’s bodyguard in Scotland).