This isn’t actually true though. Separation of Powers is an Americanism (originally French) which somehow became accepted as an iron law of how all systems work, but it isn’t and never has been.
I mean think about it for a moment – the Prime Minister is head of the executive branch and is also an MP (ie a member of the legislative branch). So are all the ministers. If we had Separation of Powers that wouldn’t be possible.
That’s always how Britain worked, we had a fairly unified governing system which self-corrected and headed off extremism in any form.
Another aspect is the idea that the judiciary must be independent. That’s closer to the British system but ultimately we didn’t have Separation of Powers there either – until 2008 the top appeal level wasn’t a court, it was a committee of the House of Lords (part of the legislature).
This would be harmless enough if ‘Separation of Powers’ was just something people say—we sort of do have something similar, to some extent, even if it’s not a principle—but typically Blair’s Labour used the misconception to push through what they called ‘modernisation’ by separating the judiciary from its tether to the other branches of government.
At the same time they massively but less-conspicuously increased its powers by entrenching their favourite principles in the Human Rights Act (and in the Equality Act) – meaning that from that point policy in those areas was largely turned over to the judges, without the twitch on the thread from the House of Lords, and it turned out the mechanism of entrenchment has carried a magic force strong enough to stop those principles from being revisited, even though we supposedly had a change of government for 14 years in the meantime.
The consequence, as Dominic Cummings has noted, is that the British immune system was destroyed and in these areas we do now have extremism. It sounds like the wrong word until you get a fiasco like this, where it suddenly becomes clear that our governing classes cannot give effect to the broad will of the country. What else would you call it?
It happened by stealth and I’m not even sure much of it was deliberate. But in a way that makes me despise what Labour did even more – the absolute carelessness with which they treated what should have been most precious.