Boris Johnson, the Brexit Prime Minister, took over for Theresa May in 2019.
May, who was a notably ineffectual Remainer who bungled Brexit took over from David Cameron after he backed the losing side on the Brexit referendum in 2016.
Cameron, in turn, took over from Gordon Brown in 2010 following a general election that produced a hung Parliament and a Tory-Liberal Democrat coalition. Cameron was one of those tedious “modernizing” conservatives known all the world over and didn’t achieve much in his reign, except to win an unexpected majority in 2015, which ironically sowed the seeds for his downfall since he saw off the threat from Nigel Farage and Ukip by promising a referendum on the European Union.
Gordon Brown, in turn, became Prime Minister without a general election in 2007, he was one of the several (there was also Canada’s Paul Martin and Australia’s Costello) finance minsters (Chancellor of the Exchequer in UK parlance) to serve a long time in anticipation of taking the big job. He took the big job from Tony Blair, however, on the eve of the Great Recession and never had much of a chance.
Tony Blair was the leader of the faction known as “New Labour”, which pitched a “Third Way” in politics between capitalism and socialism, which mostly consisted in practice of Nanny State capitalism run by a supposedly benevolent managerial class. He was supposedly cool for a while, but his reputation was badly damaged by the Iraq War.
John Major was Blair’s predecessor, serving from 1990–1997, when the Tories were shattered in a general election. His administration was marked by notably bungling and Tory infighting over Europe.
Margaret Thatcher, of course, was Major’s predecessor. A great reforming Prime Minister, she undid much of the damage done by the socialistic measures of the governments that came before her and thrashed the damned Argentines in the Falklands and was Ronald Reagan’s partner in the ultimate defeat of the Soviet Union. However, she was done in by internal treachery, with Europe being the proximate cause.
James Callaghan was Thatcher’s processor. His reign was undistinguished, running what became a Labour minority administration that was eventually heavily defeated amidst endemic strikes and inflation.
Harold Wilson, in his brief second term, came before Callaghan. The only real items of note from his second term were the corruption that marked his exit from office (the so-called “Lavender List”) and the persistent rumors that he was actually forced from office because he was a Soviet agent (see Peter Wright’s “Spycatcher”).
Edward Heath was Wilson’s predecessor. He came into office on a supposedly hard-right platform, but then turned back to interventionism and saw his government brought down in part as a result of massive strikes. He is also notable in that he was probably Britain’s only homosexual Prime Minister in the 20th Century (though this is speculation, of course).
Harold Wilson’s first term came before Heath. He presided over a minority administration followed by a majority, which was notable for withdrawing British forces from east of Suez, as the era of British Imperial power came to a close.
Alec Douglas-Home briefly served before Wilson. He is mostly notable for being a nobleman who disclaimed his Peerage in order to enter the House of Commons (though this is not a legal requirement, there has not been a Prime Minister from the Lords since the very first years of the 20th Century).
Harold MacMillian came before Home. He was much-liked and won a strong majority in his one general election, but his government was undone by scandal.
Anthony Eden came before “SuperMac.” His premiership was short and destroyed by Suez.
Winston Churchill’s second term came before Eden (who was his long-time protégé). His government undid some of Labour’s crimes, but it was also marked by Churchill’s declining health and and futile efforts to broker big superpower summits.
Clement Attlee’s socialist Labour government followed the wartime coalition. It nationalized much of industry, created the NHS, and committed many other crimes, though it did not veer so far-left as to align with the USSR.
Winston Churchill’s wartime government came before that. He saved the world.
Neville Chamberlain came before Churchill. We all know about Munich. Of him we may only say that he meant well.
Stanley Baldwin’s last government came before Chamberlain. The principal episode of this era was the Abdication Crisis.
Ramsey MacDonald formed two governments before Baldwin’s third term. First, in 1929, he formed a pure Labour government. However, after the Depression began in earnest, the Labour Party would not agree to the sort of reductions in public expenditure that orthodox economics of that day demanded, and so he formed a “National Government” with the Tories and some Liberals along with his Labour followers.
Stanley Baldwin’s second government came before MacDonald. It is mostly remembered for returning to the Gold Standard and the General Strike.
Ramsey MacDonald former the first Labour government in 1924. It was a minority administration and did not last long. It was undone in the resultant general election, in part, through a bit of trickery which claimed it was Soviet-linked.
Stanley Baldwin’s first government came before the first Labour administration. It didn’t do much before calling a general election that it lost when it turned to protectionism and sought a new mandate for it.
Andrew Bonar Law was memorably described as the Prime Minister whom “no one knew.” A Canadian by birth, he served briefly, resigned, and then died.
David Lloyd George was first a great wartime Prime Minister, leading a coalition, and then led the coalition into peacetime until he was undone, in part, by corruption (and a crisis in Turkey). He was the last Liberal Prime Minister.
Herbert Henry Asquith came before Lloyd George. He was an effective peacetime Prime Minister, presiding over the creation of the beginnings of the welfare state, but hopeless in wartime. During the war he spent much of his time writing to to his sort-of mistress, Venetia Stanley (which is one of the primary sources of records of Cabinet deliberations from that era).
Henry Campbell-Bannerman served briefly before Asquith. He won a great majority, but he was in poor health and died shortly after resigning.
Arthur Balfour took over for his uncle. His government was brief and heavily defeated.
Robert Cecil, the Marquess of Salisbury (generally known as Lord Salisbury) served before Balfour. His final term was notably marked by the Boer War and the passing of Queen Victoria.
Lord Rosebury came before Salisbury. His government was brief and didn’t do much. He was on the right, such as it was, of the Liberal Party (he was also probably a homosexual).
Gladstone’s last government came before Rosebury. This was marked by a final futile attempt to enact his ideas on Irish Home Rule into law.
Lord Salisbury served an extended term before Gladstone’s final term. This was marked by efficient Tory Administration and imperial expansion. This was also when Randolph Churchill briefly served as the Chancellor, before flaming out.
Gladstone led a brief minority government between governments led by Lord Salisbury. He continued to tilt at the Irish windmill here.
Lord Salisbury served a first term.
Gladstone served an extended term after Disraeli, having feigned retirement and gained office based upon a highly moralistic campaign attacking British foreign policy. He then proceeded to prove Lord Palmerston correct by thoroughly wrecking the Liberal Party with his ideas about Irish Home Rule.
Disraeli (eventually the Earl of Beaconsfield) served his long term before Gladstone’s second term. During his time he expanded the franchise and made Victoria the Empress of India.
Gladstone’s first administration came between Disraeli’s governments. This was marked by relatively efficient administration and a continued focus, as was long the goal of Gladstone, on economy.
Disraeli led a brief government that soon fell.
The Earl of Derby led his final brief government after Russell.
Lord John Russell, twenty years after his last spell in power, followed Palmerston.
The aged Lord Palmerston led a second government, won a sweeping majority, and continued to focus on foreign affairs.
The Earl of Derby led another brief, undistinguished, Tory government between Palmerton’s administrations.
Lord Palmerston took office admits the Crimean War and, after resolving that crisis, focused largely on foreign affairs.
Aberdeen (I forget his noble rank, but he was one) led a government that got involved in the war in Crimea, before being deposed for inefficient prosecution of the war.
The Earl of Derby led his first government before Aberdeen. It was the first Conservative administration following the fall of Peel and the division of that party into factions. It was known as the “Who? Who?” government because the aged Duke of Wellington was heard to shout that question in the House of Lords on hearing the names of the members announced.
Lord John Russell served an extended term before Derby, but his government was largely undistinguished at least insofar as I don’t remember anything in particular that they did.
Robert Peel was Russell’s processor. Peel famously repealed the Corn Law (heavy duties on food imports), an act that broke the Tory Party.
Viscount Melbourne’s second government came before Peel. He was a Whig and a favorite of Queen Victoria.
Peel briefly served as Prime Minister between Melbourne’s governments, though he did not achieve much during this time.
The Duke of Wellington served as Prime Minister for a second time for a few weeks before Peel, while Peel made his way back from Italy where he was for some reason.
Melbourne served a long first term before the Peel/Wellington government.
Earl Grey served before Melbourne, leading a Whig Administration that passed the Great Reform Bill of 1832.
The Duke of Wellington led another brief Tory government at the end of the long run of Tory regimes.
Viscount Goderich preceded Wellington, but I don’t remember anything else about his brief regime.
Canning came before him. He served one of the briefest terms of any Prime Minister before dying, having waited so long in Liverpool’s shadow.
The Earl of Liverpool was Prime Minister for fifteen years before Canning, presiding over the end of the Napoleonic Wars and the discontent that followed afterward (the “Peterloo” massacre and all of that).
Spencer Perceval served briefly before Liverpool. He is mostly notable for being the only British Prime Minister to ever be assassinated, not for political reasons as I recall, but simply by some nut.
The Duke of Portland led a brief second government before that notable mostly for serving as Prime Minister for a second time about thirty years after the first.
Grenville led a government before Portland, known as the “Ministry of All the Talents”, a brief attempt at a post-Pitt coalition government.
Pitt served a second, relatively brief term.
Henry Addington served as Prime Minister during the brief period of peace with Napoleon, between Pitt’s terms.
Pitt the Younger was appointed Prime Minister when he was twenty-two or so, and then managed to serve for about two decades, maintaining power by Royal favour, leading Britain into multiple wars against the French, and drinking two bottles of Port a day.
There were several brief Prime Ministers before Pitt. I believe it goes: Portland, Rockingham, Shelburne, but I could be wrong about the order.
Before them comes the infamous Lord North, Prime Minister during the Revolutionary War.
Before that it gets foggy. Lord Chatham (Pitt the Elder) was PM before North, but there’s someone in-between him. Before him there are a few other undistinguished nobles, Pelham, and then finally the first long-serving Prime Minister, Robert Walpole.