HENRY SINCLAIR OF SANDWICK lived in the reign of James VI From a Manuscript [Rev. James Kay] description of Dunrossness it is learned that in revenge for some insult to his servant in the house of Brew, he, on the instigation of his wife, caused the man to kill Richard Leask, son-in-law to Oliver Sinclair of Brew, when he was about to enter Sandwick Church. Upon hearing of the murder, Leask's son-in-law, Henry Dillidasse, proceeded from Orkney, where he was living, to Caithness, and having gathered together some of his friends, passed on with them to Shetland. They fell upon Henry Sinclair and his men upon a moor between Laxfirth and Lerwick, and in the melee which ensued Dillidasse shot the murderer with a pistol. Several men fell in the encounter, Henry Sinclair escaping with difficulty, while one man, Sinclair of Burray, swam over to the Island of Trondra. To this family the Island of Mousa once belonged.
In 1716 HENRY SINCLAIR, then in SANDWICK, and his spouse disponed to Robert Sinclair of Quendale 23 ½ merks land in Nether Levenwick and North and South Voe. Quendale appears as owner of Mousa in 1705.