[1] Lewis was educated at Eton College and matriculated in 1824 at Christ Church, Oxford, where in 1828 he earned a first-class in classics and a second-class in mathematics.

[1] In 1833 Lewis took on his first public role as one of the commissioners to inquire into the condition of poor Irish across the United Kingdom of Great Britain and Ireland.

[1] Lewis was then returned as Member of Parliament for Herefordshire, and Lord John Russell appointed him Secretary to the Board of Control.

There he introduced bills for the abolition of turnpike trusts and the management of highways by a mixed county board, and to define and regulate the parochial assessment.

[6] On the dissolution of parliament which followed the resignation of Lord John Russell's ministry in 1852, Lewis sought re-election in the 1852 United Kingdom general election.

[3] In 1855 Lewis succeeded his father in the baronetcy, and was elected member for the Radnor Boroughs, and Lord Palmerston made him Chancellor of the Exchequer.

[1] Historian Richard Shannon has argued that, had Lewis lived longer, he and not William Ewart Gladstone might have come to lead the Liberal Party.

[1] A major early work by Lewis was Remarks on the Use and Abuse of some Political Terms (London, 1832), written under the influence of John Austin.

In 1835 he published an Essay on the Origin and Formation of the Romance Languages (re-edited in 1862), criticism of François Juste Marie Raynouard's theories on Provençal.

In 1859 Lewis published the Essay on Foreign Jurisdiction and the Extradition of Criminals, topical after the Orsini affair and the trial of Simon François Bernard.

While his friend Abraham Hayward ran the Law Magazine, he wrote in it frequently on subjects including secondary punishments and the penitentiary system.

This venture into scholarship soured when he advised the British Museum on a purchase of manuscript copies by Konstantinos Minas (also known as Constantin Minadi, or Minoïde Mynas).

[1] Lewis's large circle of friends included Edmund Walker Head, George and Harriet Grote, the Austins, Lord Stanhope, John Stuart Mill, Henry Hart Milman, and the Duff Gordons.

[10] A large monument was built in his memory in the small village of New Radnor, Powys and still stands today, as does a statue in front of the Shirehall, Hereford.