The brief introduction states that England is ruled by a fascist military force called The Guardians. In fact the political setup is rather more nuanced. The elderly Prime Minister Sir Timothy Hobson (Cyril Luckham) is pious, ponderous and paternalistic, more Malcolm Muggeridge than Mussolini. He has some authority but is beholden to a mysterious general whose opinions are conveyed by a go-between, the hard and ruthless Secretary to the Cabinet Dennis Norman (Derek Smith).
The first few episodes concern Government tensions and power struggles and are very good. The most thoughtful one is the second, dominated by a lengthy argument in a gentleman's club between Sir Timothy and a liberal minded old chum. Sadly it then appears to have run out of political ideas, the focus switching to less important and generally uninteresting characters. Sir Timothy fails to appear in four episodes, some of them little more than soap opera. The ending is dramatic, although far fetched.
Other reviewers have drawn parallels with various British governments so I'll feel free to add my tuppence worth. The only recent experience of authoritarian rule in Britain was during the pandemic and the imposition of draconian and often absurd decrees, and where Government was largely sub contracted to a group of medical panjandrums. In Parliament the only significant opposition came from a few liberty lovers on the Right of the Conservative Party.