[1] Bernard Burke, in his a Genealogical and Heraldic Dictionary of the Peerage and Baronetage of the British Empire, agrees with Roland Saint-Clair and says that Henry Sinclair was "in reality" the fourth holder of the title of Lord Sinclair.

Immediately after the death of his father, an Act was passed by the Scottish Parliament in his favour and which recognised him as "Chief of yat blude" and willing "yarfor that he be callit Lord Saintclair in tyme to cum", dated 26 January 1488–89.

This Act was only a recognition of the Barony of St. Clair existing in the person of his ancestor, Henry II Sinclair, Earl of Orkney and did not constitute a new creation.

On 28 May 1489 Lord Sinclair received several grants including a 13-year lease of Orkney and Shetland, the custody of Kirkwall Castle with the fortalices, and the Justicary, Folderie and Balliatus for 13 years.

[2] Lord Sinclair was made Master of the Artillery on 13 March 1510, for a fee of £100 a year, deducted from his Orkney accounts.