The ability of "rule of law" to constrain the arbitrary actions of state security has always been a problem, in every country, and is fatally compromised in the UK by colonialism (use of military as police in Northern Ireland, and before that various crimes of Empire that we're not supposed to know about) and racism (fundamentally a large section of the public wants it to be possible to arbitrarily deport immigrants without due process of law, and is prepared to burn down as much rule of law as necessary to achieve that)