155.Section 20 interprets terms used in this Chapter.
“External communications”: under the Interpretation Act 1978, the term “British Islands” means the United Kingdom, the Isle of Man and the Channel Islands.  The use of the term in this Chapter therefore means that communications sent between the UK and the Islands, or between the Channel Islands and the Isle of Man, are not treated as external.
“Related communications data”: the term “communications data” is defined for the purposes of Chapter II in Section 21(4).
Commentary on Sections “Relevant judge” is explained in subsection (11). Section 20