My own debt to O'Brien is for Edmund Burke - an abridged version of his book The Great Melody: A Thematic Biography and Commented Anthology of Edmund Burke.
Burke is often claimed by English Conservatives as their intellectual ancestor, but that suggests they do not know much about him. As Christopher Hitchens has said:
More than that, Burke supported the American revolutionaries and was for many years the great political ally and intellectual support of the Whig leader Charles James Fox. They fell out after the French Revolution, which Burke condemned while Fox insouciantly looked forward to its spreading to Britain. That falling out took place, very publicly, during a Commons debate, and O'Brien description of the exchanges is memorable.
Edmund Burke was neither an Englishman nor a Tory. He was an Irishman, probably a Catholic Irishman at that (even if perhaps a secret sympathizer), and for the greater part of his life he upheld the more liberal principles of the Whig faction.
He was an advanced opponent of the slave trade, whose "Sketch of a Negro Code" was written in the early 1780s, and who before that had opposed the seating of American slaveholders at Westminster. His epic parliamentary campaign for the impeachment of Warren Hastings and the arraignment of the East India Company was the finest example in its day of a battle against pelf and perks and privilege.
Burke's defection from the Whig campaign has generally been seen as apostasy, but O'Brien argues that Burke was consistent because of his Catholicism (or at least his Catholic sympathies). He sided with the Whigs because of their support for religious toleration, but joined the Tories because of the Jacobins anti-clericism.
Whatever the truth of this, one important fact stands out. Burke was right and Fox was wrong.
I had always assumed that Burke's Reflections on the Revolution in France was written as a response to French Revolutionary terror. In fact it was published in 1790, before the blood began to flow and when much English Whig opinion, like Fox, were broadly sympathetic to the Revolutionaries and their aims.
Burke's foresight - his realisation that terror would come in the wake of revolution - reminds me of the way that anarchist thinkers like Bakunin realised the dictatorship inherent in Marx's call for proletarian revolution.
British Liberals probably feel an instinctive sympathy for the French Revolution, but we should not forget that Karl Popper and Isiah Berlin, perhaps the greatest Liberal philosophers of the 20th century, were both profoundly anti-revolutionary thinkers.
Anyway, read O'Brien and read Burke. Hitchens quotes the unimpeachably radical William Hazlitt as saying:
It has always been with me a test of the sense and candour of any one belonging to the opposite party, whether he allowed Burke to be a great man.