[3] Nony's portrait by Sir Thomas Lawrence (commissioned by John Croker) is in the collection of the Albright-Knox Art Gallery in Buffalo, New York.

In 1804 he published anonymously Familiar Epistles to J. F. Jones, Esquire, on the State of the Irish Stage, a series of caustic criticisms in verse on the management of the Dublin theatres.

[2] Equally successful was the Intercepted Letter from Canton (1805), also anonymous, a satire on Dublin society in the guise of a report on the manners of the Chinese at Quang-tchen on the "Li-fee".

The acumen displayed in his Irish pamphlet led Spencer Perceval to recommend him to the Duke of Wellington, who had just been appointed to the command of British forces in the Iberian Peninsula, as his deputy in the office of chief secretary for Ireland.

The speech which he delivered on 14 March 1809, in answer to the charges of Colonel Wardle, was regarded as able; and Croker was appointed to the office of first secretary to the Admiralty, which he held without interruption under various administrations for more than twenty years.

[7][6]: 472 In 1816 he reduced the size of the Royal Navy, and over 1,000 ships were decommissioned and placed in the Reserve Fleet (United Kingdom) or "laid up in ordinary" at various British naval bases.

[citation needed] In 1827 he became the Member of Parliament for Dublin University, having previously sat successively for the boroughs of Athlone, Yarmouth, Bodmin and Aldeburgh.

Many of his political speeches were published in pamphlet form, and they show him to have been a vigorous and effective, though somewhat unscrupulous and often virulently personal, party debater.

It also reacted unfavourably on Croker's reputation as a worker in the department of pure literature by bringing political animosities into literary criticism.

Hill observed that Croker was "not deeply versed in books", was "shallow in himself", did not understand Johnson's strong character, seemed inadequately acquainted with Johnson's writings, failed to grasp Boswell's flair as a biographer, and "is careless in small matters, and his blunders are numerous": Croker was occupied for several years on an annotated edition of Alexander Pope's works.

[2] Croker was generally supposed to be the original from which Benjamin Disraeli drew the character of "Rigby" in Coningsby, because he had for many years had the sole management of the estates of the Marquess of Hertford, the "Lord Monmouth" of the story.