He enjoyed a salary for defending the policy of Lord North's government, and held the lucrative post of London agent to Mahommed Ali, nabob of Arcot.
In February 1785 he delivered one of the most famous of all his speeches, that on the nabob of Arcot's debts.
In a temperate and learned speech, based on Fox's declaration against constitution-mongering, he supported both the enfranchising and the disfranchising clauses, and easily disposed of the cries of "corporation robbery," "nabob representation," "opening for young men of talent," &c. The following year (1832) found Campbell solicitor-general, a knight and member for Dudley, which he represented till 1834.
The name of nawdb, corrupted by Europeans into " nabob," appears to be an invention of the Moguls to express delegated authority, and as such it is the highest title conferred upon Mahommedans at the present day, as maharaja is the highest title conferred upon Hindus.
A classical education and the instincts of family pride saved him from both the greed and the vulgar display which marked the typical "nabob," the self-made man of those days.