I read the first instalment of Volume 1 of Halevy's history, in which he deals with 'political institutions'. He begins with the bureaucracy, then treating the Army, Navy, 'judicature', the English people's customary liberties and only last getting onto the factional and divided state of the House of nd Commons, which had sunk in public esteem by 1815. Both parties, Tory and Whig, had forfeited any trust that they could reform corruption or make the legislature more representative of the country.
The first question is how far the unspoken British Constitution met Montesquieu's ideal requirement of a separation of powers between different branches of government. Halevy finds that it did not--but that the blurring, in practice, between these arms tended everywhere to strengthen public opinion and Parliament to the detriment of any executive with pretensions to despotism. Britain was the only country in Western Europe to uphold a right to publish without preliminary censorship; magistrates upheld the right of meeting, which could not be dissociated in fact from the proscribed 'right' of association; any party claiming a wrong could address a petition to his sovereign. It had been the Tories under Pitt who had been the party of Adam Smith, of free trade, economic (or what we would now call 'administrative') reform and constitutional radicalism, in their creation of a host of peerages overturning the natural Whig predominance in the House of Lords. Halevy describes interestingly how the seeds for the bigger upsurge of Parliamentary reform in 1832 were sown, by Tories as much as Whigs, by reforms going back as far as 1770 (when MPs lost the right to rule in disputed elections).
Halevy knows a lot, and writes clearly and attractively. There are many strings to his bow: he likes the political intrigue, the friction between personalities, but also grasps change as a function of the emergence of new social forces (the manufacturing interest in the northern cities, the 'nouveau riche' class of East India Company nabobs and City bankers). He has an interesting thesis, suggested by Edmund Burke: that Britain steered its path to reform more consensually than any other nation because the nineteenth saw the solidifying of an oligarchical class of statesmen who shared a culture, language and code of conduct, however they may have been on opposite sides politically.