GCHQ [1985]

House
of Lords held not for courts to question government’s discretion to decide
whether natural security considerations outweighed considerations of fairness
in particular case.
Courts
do not have necessary information.
Lord
Diplock:
Grounds
for JR of administrative action could be classified under three heads:
illegality, irrationality and procedural impropriety.
Others,
incl. perhaps proportionality, might be added later.
[Note
that Diplock was employing term ‘irrationality’ here to mean same thing as Wednesbury unreasonableness in the
substantive sense.
Term
‘irrationality’ now often used as synonym for Wednesbury unreasonableness in the substantive sense.]