(1) There shall continue to be a Government
Communications Headquarters under the
authority of the Secretary of State; and, subject to
subsection (2) below, its functions shall be (a)
to
monitor
or
interfere
with
electromagnetic, acoustic and other
emissions and any equipment producing
such emissions and to obtain and provide
information derived from or related to
such emissions or equipment and from
encrypted material; and
(b)
to provide advice and assistance about—
(i)
languages, including terminology used
for technical matters, and
(ii)
cryptography and other matters relating
to the protection of information and other
material,
to the armed forces of the Crown, to Her
Majesty’s Government in the United Kingdom or
to a Northern Ireland Department or to any other
organisation which is determined for the purposes
of this section in such manner as may be specified
by the Prime Minister.
(2) The functions referred to in subsection (1)(a)
above shall be exercisable only—
(a)
in the interests of national security, with
particular reference to the defence and
foreign policies of Her Majesty’s
Government in the United Kingdom; or
(b)
in the interests of the economic wellbeing of the United Kingdom in relation
to the actions or intentions of persons
outside the British Islands; or
(c)
in support of the prevention or detection
of serious crime.
…
5 Warrants: general.
(1) No entry on or interference with property or
with wireless telegraphy shall be unlawful if it is