21Powers of seizure etc
(1)A police or customs officer who is exercising the power of search conferred by section 14 may seize and detain anything found in the course of the search.
(2)A police or customs officer who is exercising a power of search conferred by section 15, 16 or 17 in relation to any premises may—
(a)seize and detain or remove any item found on the premises;
(b)take copies of or extracts from any document or record found on the premises.
(3)An officer to whom a document or record has been produced in response to a requirement imposed under section 20 may—
(a)seize and detain or remove that document or record;
(b)take copies of or extracts from that document or record.
In this subsection “document” includes anything falling within paragraph (a) or (b) of section 20(3).
(4)The powers under this section may be exercised only—
(a)for the purposes of determining whether a relevant offence has been committed, or
(b)in relation to an item that the officer concerned reasonably believes to be relevant evidence.
(5)Nothing in this section confers power on an officer to seize an item that is an excluded item (see section 24).