Judicial review available for unreasonable/irrational decisions
'A confession of a crime is no good without a complainant.'
Answer:
Absolute rubbish. Why don't you sit in a court for a week or so and find out? Plenty of people get convicted on their own confession in interview when the victim refuses to give evidence.
'Incidentally, how could McKinnon's lawyers "launch a judicial review of the DPP". They could request one, but without any evidence that the DPP has acted unlawfully they have no chance of getting one.'
Answer:
The above poster clearly does not completely understand the rules of evidence, let me further enlighten their expertise on the subject of judicial review of administrative action.
If a government department (here the CPS) take a decision that is irrational or unreasonable then that decision can be judicially reviewed. You do not, as the poster asserts, have to show that the decision was purely unlawful.