He had followed with enthusiasm the whole course of the Oxford Movement; and in the congregation to which he belonged (St John's Episcopal Church, Aberdeen) he had supported his clergyman, Patrick Cheyne, throughout a prosecution in regard to eucharistic doctrine, which had weighty consequences, for it led to the charge and prosecution of the bishop of Brechin, Alexander Penrose Forbes, and the intervention of Pusey and Keble in defence of that prelate.
[2] Clear and unaffected in style, this work is learned and exact, but it suffers somewhat from the fact that his extreme scrupulosity as to literal truth caused him to hold too severely in check the wit and liveliness which were so conspicuous and charming in his conversation.
As an historian he was determined to be fair, albeit he is at no pains to conceal (what he was proud of) his enthusiastic toryism and his profound attachment to the Scottish Episcopal Church.
In the preface, Grub acknowledges the help he had received from Joseph Robertson and Norval Clyne; he regrets that for the history of the Roman Catholic church after the Reformation he had not been able to obtain more accurate materials; and he says that the work had occupied him more than nine years.
In spite of the more recent researches on the Celtic period of Scottish history, the book is by no means out of date; but it is unfortunate that no second edition of it was called for until Grub was too old to undertake the labour of preparing one.
To the Aberdeen Philosophical Society, he contributed the Life of Bishop Elphinstone; The Life of Bishop Burnet, and his Character as a Historian and Biographer; Dr. James Beattie and his Friends; The Antiquities of Dunkeld; Froude's History and Mary, Queen of Scots; Elgin Cathedral; Review of the Evidence as to the Complicity of Queen Mary in the Murder of Darnley; and, in concert with his lifelong friend and companion, Norval Clyne, The Ecclesiastical and Baronial Antiquities of the Cathedral of Brechin and Castle of Edzell.