Immediately on his return he persuaded Robert Reid, the bishop of Orkney, then Lord President of the Court of Session, to make certain statutes for the abbreviation of the processes and the reform of other abuses.
He was content to retain the temporalities of his bishopric, and, as president of the court of session, he made it his duty to see that proper regard was paid to the laws in actual force, whether they favoured Protestants or Catholics.
Thus, when the queen sought his advice in regard to the prosecution of several Catholics who had observed the mass, he advised "that she must see her laws kept, or else she would get no obedience".
"The bishop", he says, "answered cauldlie, 'Your grace may consider that it is neither affection to the man [Knox], nor yet love to his profession, that moveth me to absolve him; but the simple truth, which plainly appears in his defence'".
[13] On 20 February 1564, Queen Mary applied to Elizabeth for a safe-conduct for Sinclair to go into France, that he "might seek cure and remedie of a certain maladie".
It is supposed that John, rather than Henry, was the author of Sinclair's Practicks, a legal work contained in manuscript in the Advocates' Library, Edinburgh.
and, following him, Thomas Tanner (Bibliographia Britannica) split this Sinclair into two persons, one of them being represented as dean of Glasgow and lord of session and nephew of the bishop of Ross.
The nephew is credited by Dempster with the following legal works: Legum Romanorum ad Leges Scotiæ Municipales Reductio, Lib.
i. Henderson wrote in the Dictionary of National Biography that "These appellations are doubtless all paraphrastic amplifications by Dempster of the full title of the Practicks above referred to".
[15] Sinclair supplied descriptions and illustrations of Scottish animals to the Swiss naturalist Conrad Gesner for inclusion in his Historiae Animalium.