91Exercise of powers
(1)Except as provided in subsections (2) and (3), the powers mentioned in section 89(4) may be exercised only in tidal waters in the United Kingdom or in external waters.
(2)The powers may in addition—
(a)in the case of a suspected offence under this Part committed in a British-registered ship while it is on the high seas, be exercised in relation to the ship on the high seas;
(b)in the case of a suspected offence under section 78 committed on a structure or other object within waters in a designated area, be exercised in relation to the structure or other object within those waters;
(c)in the case of a suspected offence under section 79 committed in a ship within an area of the high seas prescribed for the purposes of that section, be exercised in relation to the ship within that area of the high seas.
(3)Subsection (2) does not apply so far as the powers are exercisable by virtue of a written authorisation issued by OFCOM.