Sir Robert Gordon, who lived from 1580 to 1656 - more than 150 years after Harpsdale - wrote the only surviving narrative of the battle in his Genealogical History of the Earldom of Sutherland. He set it down in the seventeenth century, drawing on family papers, oral tradition, and a Sutherland perspective that was not, it must be said, neutral. Gordon was a kinsman of the earls of Sutherland and his book is an argument for the dignity of his line. His account is brief: in the days of Robert, Earl of Sutherland, Angus Dow Mackay invaded Caithness, the inhabitants assembled, and they fought at Harpsdale with great slaughter on either side. The report of the slaughter reached King James I, who came north to Inverness to deal with the Highland chiefs who could not, evidently, be trusted to govern themselves. The king's arrival in the north transformed what would otherwise have been a forgotten clan skirmish into something more politically consequential.

James I of Scotland had been crowned in 1424 after spending eighteen years as a prisoner in England. He returned with a project: to bring royal authority back to a kingdom that had run loose during his captivity. In spring 1427 he summoned a Parliament at Inverness, ostensibly to consult on the state of the Highlands, in fact to seize control of them. The chiefs came - Highland custom required it - and the king arrested them. Alexander MacDonald, Lord of the Isles, was among them; so was his mother Mariota, Countess of Ross, and Angus Dow Mackay himself. Two prisoners were tried, condemned, and beheaded; one of them had murdered the previous Lord of the Isles, though he claimed he had done so on the king's orders. The others were scattered into various royal castles. Some died there. Some were eventually released. This was governance in the early Stewart manner: invitation, betrayal, execution.

Angus Dow Mackay, hearing that the king was at Inverness, came down from Strathnaver to submit himself. He brought his son Neil - then fourteen years old - and offered the boy as a pledge of future obedience. The king accepted the submission and sent Neil Mackay to be held on the Bass Rock, the great volcanic plug in the Firth of Forth that the crown used as a state prison. The boy lived there long enough that he was always afterwards called Niel-Bass Mackay - Neil of the Bass - by his own people. He returned eventually to Strathnaver, where his descendants were the Mackay chiefs through the centuries that followed. A fourteen-year-old hostage on a sea-rock at the opposite end of the country was the price of his clan's freedom and his father's life. The Bass Rock can still be seen from the East Lothian coast, a sheer-sided white pillar in the sea, full of gannets in summer. Whatever Neil Mackay made of his years there, he kept it to himself.

Achardale, the modern name for Harpsdale, is a quiet stretch of farmland in the Caithness flow country, about eight miles south of Thurso along what is now the B870. There is no monument, no battlefield centre, no marked field. The little river Thurso runs nearby; the road goes past steadings and barns and forestry plantations. The land has been farmed and grazed and drained continuously since the fight, and whatever physical traces the battle left have long been ploughed under. What remains is the name in Sir Robert Gordon's book, and an entry in a chronicle of the conflicts of the clans, and the memory in the families of the Mackays and the Gunns that something terrible happened here, six hundred years ago, between people whose great-grandchildren still live in the same valleys. The dead were buried where they fell. The valley itself is the memorial.