The King is not above the law - he is subject to the judgements of the courts as is any other citizen, even though it is nominally 'the King's Justice'. And it has been that way ever since Henry II set up the circuit court system and promised to be bound by it's judgements, although various monarchs have broken the undertaking down the centuries. Before that, if you wanted justice you had to seek out the King and petition him personally, which was time consuming for both parties.
Parliament is above the law, inasmuch as Parliament is the supreme arbiter of its own actions and it's decisions 'are not to be questioned or disputed in any place' [Bill Of Rights]. The original reason for this was to prevent its decisions being overturned by a justice suborned by the King.
The decisions of government ministers are subject to review by the courts, because the Minister acts not in his capacity as a Member of Parliament, although he is usually that as well, but as a Minister of the Crown appointed, nominally by the King, in practice by the Prime Minister, using the Royal Prerogative.
The CPS, also known as the Can't Prosecute Service and the Cr*p Prosecution Service was set up a few years ago following some high-profile miscarriage of justice cases. Previously such decisions had been in the hands of the police. The CPS is supposed to form an independent judgement as the whether a prosecution would be 'in the public interest'. They pay peanuts and, consequently, hire monkeys.