First of the Stanley Lords of Mann, and the name borne by both the grantee of 1405 and the son who put the Island's laws into writing.

Henry IV had granted the Island to Henry Percy, Earl of Northumberland. On Percy's treason the King seized it back, and in 1405 granted it to Sir John Stanley for life. That grant was surrendered, and in 1406 the King made a fresh grant to Sir John and his heirs and assigns, subject to the service of rendering two falcons to the King of England on the day of his coronation. The Chronicle of Man gives the date as 1403, which the Manx Society editor judged incorrect. Chaloner, who also gives 1403, describes him as Treasurer of the King's household, and elsewhere he appears as Lieutenant of Ireland. The Island had first been ordered to be seized into the hands of Sir John Stanley and Sir William Stanley for the King's use only.

The grant was made before the Earl of Northumberland was attainted, which left the Stanley title of doubtful legality. The defect went unnoticed until Elizabeth's reign, when the dispute broke out between the heir male and the heirs general. In the litigation of 1608 between the Earl of Derby and the Earls of Salisbury and Suffolk, the judges found that the grant to Sir John Stanley was warranted by the common law of England, and decided for the Stanleys. The succession itself was settled on the same ground, in favour of the heirs general. From 1405 to 1829 the charter of Henry IV was, in the words of the Manx Society's editor, the helm of the kingdom of Man and the Isles.

It was the second Sir John Stanley who made the record. Coming to the Island in 1417, he assembled the worthiest of the land to meet his Deemsters and declare what was the law and the constitution of old time, and had it committed to writing. Two of his earliest documents survive in Castle Rushen, and a facsimile of that of 18 January 1417 was printed by the Manx Society. Until then the law had been breast law, locked in the memories of the Deemsters and Keys, and the Manx Society's editors were still complaining in the 1870s that the early statutes had been imperfectly printed.

He returned in 1422 and held a court at the Hill of Reneurling, called Cronk Urleigh, on the Tuesday after the Feast of St Bartholomew, described in the record as before our doughtful lord, Sir John Stanley, King of Man and the Isles. The ecclesiastical barons were summoned to do fealty for their holdings. Three submitted. The five who were not in the Island were called and did not come, and their Manx possessions were confiscated. In the same assembly the Deemsters and Keys declared that there had never been twenty-four Keys in certainty since they were first called Taxiaxe. They also told him how a king should appear on a Tynwald day, in his royal array, by the prerogatives and regalities of Mann, with his sword borne before him point upward. The sword of state carried before him at that first Tynwald is still kept in the Rolls Office.

He brought over Michael Blundell of Lancashire as Governor, sent John Fasakerly as Lieutenant in 1418, and later Henry Byron in 1428. A nineteenth-century editor judged that under him the liberties of the Manx church were curtailed and its bishops became the nominees of the Lord of the Isle, anticipating in Man by a century the royal supremacy asserted in England under Henry VIII.