He served as the British Minister to the United States from 1857 to 1859, Netherlands from 1859 to 1860, Russia from 1861 to 1864, Prussia from 1864 to 1866 and as the Governor of Madras from 1866 to 1872.

Due to his fluency in multiple languages, Napier's lack of educational qualifications was overlooked and he entered the diplomatic service in 1840.

He served as the Acting Ambassador for a period of eighteen months in Naples, when Italy was embroiled in the Sicilian insurrection.

[1] An aristocratic haughtiness regarding the local populace infuses his writing, dismissing the skills of more than one artist, and in reactionary fashion, the revolutionary instincts of the masses.

In the preface, he writes: It was the fortune of the author to hold a diplomatic employment at the Court of Naples, during a period in which the appropriate pastimes of that pleasant city were discarded for the illusions and regrets of political change.

These transactions, of which the melancholy issue is notorious, were of a nature to engross and often to darken the thoughts of one, who had an intimate knowledge and a foreboding view of the revolutionary drama; the resources of society were limited by the suspicions and passions which altered and envenomed the conversation even of cultivated men; and the author was induced, alike by necessity and taste, to expend his relaxation and recover his serenity in the study of the local Arts.Napier's handling of affairs as acting ambassador in Naples impressed the then Secretary of State for Foreign Affairs, Lord Palmerston.

The abolitionist Charles Sumner and elements of the Northern press accused the British minister of being a pro-slavery partisan.

Critics at the Foreign Office accused him of "giving up everything the United States can wish for, even before they ask it", which for them explained Napier's immense popularity with Washington's influential residents.

Despite being at odds with different viceroys over financial issues throughout his tenure, Napier was able to resolve disputes in an amicable manner due to the friendly relations he had with Sir John Lawrence and well as his successor, Richard Bourke, 6th Earl of Mayo.

When the Earl of Mayo was assassinated in the Andamans on 8 February 1872, Napier was designated to act as the Viceroy of India and he served for a short time before being relieved by Lord Northbrook.

Lord Napier is sixty-two years old, considerably above middle size, strong, healthy, with calm, handsome face, gray hair and whiskers, an early riser, very often a late goer to bed, gifted with inexhaustible energy, tact common sense and acuteness of judgement.