He took his notes using an improvised form of shorthand, then prepared type for printing without a written copy.
As the paper gained ground Garnett's share in the editorial side increased, and in January 1844 he became sole editor on the death of his partner Taylor, a position which he held until his retirement in 1861.
The Guardian was widely read by Tories and Anti-Corn Law Leaguers, who had little sympathy with its moderate liberal politics.
The most important was on the occasion of the expulsion of Thomas Milner Gibson and John Bright from the representation of Manchester in 1857, which was almost entirely due to his initiative.
His nephew was Richard Garnett (1835–1906), the author of his entry in the Dictionary of National Biography (1900), who says, "As a man he was upright and benevolent, but singularly averse to display; as a writer for the press his principal characteristics were strong common-sense and extreme clearness of style.