The Private Security Industry Act 2001 states:

Conduct Prohibited without a Licence

(1) Subject to the following provisions of this Act, it shall be an offence for a person to engage in any licensable conduct except under and in accordance with a licence.

(2) For the purposes of this Act a person engages in licensable conduct if

(a) he carries out any designated activities for the purposes of, or in connection with, any contract for the supply of services under which

(i) he,

(ii) a body corporate of which he is a director, or

(iii) a firm of which he is a partner,

is or may be required to secure that any such activities are carried out;

(b) in the course of any employment of his by any person he carries out any designated activities for the purposes of, or in connection with, any contract for the supply of services under which his employer is or may be so required;

(c) he carries out any designated activities in accordance with directions given to him by or on behalf of a person to whom his services are supplied (whether or not for the carrying out of any such activities) by

(i) a body corporate of which he is a director,

(ii) a firm of which he is a partner,

(iii) a person by whom he is employed, or

(iv) a person to whom he supplies his services under a contract for the purposes of which, or in connection with which, he is or may be required to work in accordance with the directions of another;

(d) he acts

(i) in the course of any employment of his by any person, or

(ii) in accordance with any directions given as mentioned in paragraph (c),

as the manager or supervisor of one or more individuals required in the course of their employment to engage in licensable conduct falling within paragraph (b);

(e) he acts

(i) in the course of any employment of his by any person, or

(ii) in accordance with any directions given as mentioned in paragraph (c),

as the manager or supervisor of individuals who are required in accordance with any such directions to engage in conduct which would be licensable conduct falling within paragraph (b) if they were required to engage in that conduct as the employees of the person to whom their services are supplied;

(f) he is the director of any body corporate or the partner of any firm at a time when another of the directors or partners of the body or firm, or any employee of the body or firm, engages in licensable conduct falling within any of paragraphs (a) to (e);

(g) he is the employer of an individual who in the course of any employment of his with that employer carries out any designated activities subject to additional controls;

(h) in the course of any employment of his, or for purposes connected with his being a director or partner of a body corporate or firm, he carries out designated activities subject to additional controls;

(i) in the course of any employment of his by any person he acts as the manager or supervisor of one or more individuals the duties of whose employment involve the carrying out of any designated activities subject to additional controls; or

(j) in circumstances in which it is proposed to impose a charge for the release of immobilised vehicles, he carries out on his own behalf or on behalf of another person any designated activities consisting in activities to which paragraph 3 of Schedule 2 (immobilisation of vehicles) applies.

(3) In this Act “designated activities” means such of the activities of a security operative as are for the time being designated for the purposes of this section by an order made by the Secretary of State; and an order under this subsection may designate different activities for the purposes of different paragraphs of subsection (2).

(4) For the purposes of this section a person shall not be treated as acting as the manager or supervisor of an individual by reason only of his giving directions to that individual in a case in which—

(a) the directions are given on behalf of a person to whom the individual’s services are provided under a contract for services, and

(b) the person who under the contract provides the individual’s services or another person acting on his behalf, acts as the manager or supervisor of that individual in relation to the activities carried out by him in accordance with those directions.

(5) Schedule 2 (which defines the activities that are to be treated as the activities of a security operative for the purposes of this Act and those which, so far as they are designated, are subject to additional controls) shall have effect.

(6) A person guilty of an offence under this section shall be liable, on summary conviction, to imprisonment for a term not exceeding six months or to a fine not exceeding level 5 on the standard scale, or to both.

source: http://www.legislation.gov.uk/ukpga/2001/12/section/3