16(1)This paragraph applies if the appropriate authority is required by virtue of—
(a)any determination made by that authority under paragraph 6(2) (whether following the recording of a complaint or on a reference back under paragraph 5(2)) or under paragraph 8(4), or
(b)any determination made by the Commission under paragraph 15,
to make arrangements for a complaint or recordable conduct matter to be investigated by the appropriate authority on its own behalf.
(2)This paragraph also applies if—
(a)a determination falls to be made by that authority under paragraph 10(4)(b), or 11(3)(b) or 14(2) in relation to any recordable conduct matter; and
(b)the appropriate authority determine that it is necessary for the matter to be investigated by the authority on its own behalf.
(3)Subject to sub-paragraph (4), it shall be the duty of the appropriate authority to appoint—
(a)a person serving with the police (whether under the direction and control of the chief officer of police of the relevant force or of the chief officer of another force), or
(b)a member of the National Criminal Intelligence Service or the National Crime Squad,
to investigate the complaint or matter.
(4)The person appointed under this paragraph to investigate any complaint or matter—
(a)in the case of an investigation relating to any conduct of a chief officer, must not be a person under that chief officer’s direction and control; and
(b)in the case of an investigation relating to any conduct of the Commissioner of Police of the Metropolis or of the Deputy Commissioner of Police of the Metropolis, must be the person nominated by the Secretary of State for appointment under this paragraph.