Queen Elizabeth II is dead; aged 96, and having served on the throne for 75 years, she died at her Scottish estate at Balmoral. Prince Charles has ascended to the throne, and gone with the name King Charles III, despite concerns that the name has less than fortuitous historical connotations.
This post will not be a judgment of her reign, the choices she made or the legitimacy or otherwise of the institution she was at the head of. (In short, I am not a believer in the institution of hereditary monarchy, though having a nonexecutive head of state on a longer term than individual governments does appear to have a salutary effect on the institutions of state, though this is a much longer discussion for another place and time; meanwhile, the British Empire was responsible for numerous colonial evils, some of which happened with her as its figurehead.)
Queen Elizabeth II reigned for just over 75 years—¾ of a century; it is estimated that 90% of the people alive today were born during her reign. Which has the effect that next to nobody (in her dominions, or indeed anywhere else) remembers a time when she was not on the throne. From a subjective human point of view, she may as well have always been there, like some kind of ancient god, impassively presiding over the tumult of change. And her reign started with the remnants of the British Empire dissolving like a soluble aspirin, and ended with a Britain punch-drunk on imperial nostalgia and tabloid jingoism rejecting its destiny as a medium-sized, prosperous European country, declaring that it was going to reclaim its globe-spanning destiny, and promptly falling flat on its face. In the future it is quite likely that the notion that England's half-millennium of glory (or, indeed, non-obscurity) was bookended by the two Elizabethan eras will be a glib truism.
Given Britain's current state (bleeding from Brexit wounds, permanent austerity as a moral imperative, soaring energy bills, and the aftermath of a leadership contest where the contenders sought to demonstrate superior cruelty before an audience of Britain's most vicious pensioners), the kicking out of this symbolic pillar of certainty will have interesting effects. Unlike the Tory leadership contest, the new monarch is already foreordained by succession laws. It is unlikely that Charles will recuse himself from intervening in the way his mother did: all accounts suggest that he is determined to give his subjects the benefit of his wisdom, so we may soon see an all-homeopathic NHS and mandatory Palladian colonnades on all new buildings or something. Whether Charles III will acquire an aura of dignity as his mother had is also in question. He has been around for almost as long, though in considerably different circumstances.
There has been an assumption that the end of Elizabeth II's reign would be a natural boost for the republican cause: most affection for the monarchy was not for the institution itself, but its figurehead (whom some have called “Our Queen and Pleasant Nan”), and would not transfer to her large adult son, and a lot of soft monarchist sentiment would evaporate. On the other hand, given the traumatic nature of the present moment in Britain, it is conceivable that some in England will dig in harder, and dream into being King Charles III as the benign symbol of stability he otherwise wouldn't be, just to have something to hold on to. This may not play out quite as well north of the Scottish border, and Australia is probably not unlikely to become a republic of some sort within the next decade or two.