Thanks for the answer! Though that still leaves the question of how this whole thing started in the first place.
Basically, after the Great Continental War (think a cross of WW1 and WW2, all over the span of 12 years, while the British are facing a Blitz equivalent for most of that time), the UK was led largely by Tory governments after Labour discredited themselves when the war ended. After Clement Atlee, who in this TL was a Tory, the premiership landed in the hands of Lord Salisbury, an arch-reactionary, and after he was pushed out of power due to a fracas over migration, Alan Lennox-Boyd, another arch-reactionary. During this period, Labour was increasingly moribund and was fracturing into various factions, but some of those factions were aligning with the remnants of the Liberal Party. Led by Roy Jenkins, this Liberal Alliance promised economic prosperity and social change after decades of war and economic depression. In 1966, the Alliance, led by "Woy," won Westminster in a landslide, bringing about an era of revival for the United Kingdom. Despite multiple challenges, including the inglorious end of Jenkins' leadership in his brutal reaction to the Bengali War of Independence, both the Tories and Labour doubled down on increasingly unpopular positions (hardcore social conservatism for the Tories and loony leftism for Labour) and failed to capitalize on these missteps. Eventually, Glenda Jackson took control of the Alliance in the 90s and reformed the various parties within the Liberal Alliance into a single Liberal Party, often called the Green Machine, marked by patronage, clientelist politics, and semi-competent management of the country, and indeed the Empire. There have been low points - the Liberals fell to "only" 54% in the polls last year due to the unpopularity of the American War - but so far, the Green Machine has remained intact and able to distribute patronage for years to come, buoyed by decades of rapid economic growth and the revival of the UK on the world stage.