Official Secrets Act 1989

4 Crime and special investigation powers

(1) A person who is or has been a Crown servant or government contractor is guilty of an offence if without lawful authority he discloses any information, document or other article to which this section applies and which is or has been in his possession by virtue of his position as such.

(2) This section applies to any information, document or other article—

(a) the disclosure of which—

(i) results in the commission of an offence; or

(ii) facilitates an escape from legal custody or the doing of any other act prejudicial to the safekeeping of persons in legal custody; or

(iii) impedes the prevention or detection of offences or the apprehension or prosecution of suspected offenders; or

(b) which is such that its unauthorised disclosure would be likely to have any of those effects.

(3) This section also applies to—

(a) any information obtained by reason of the interception of any communication in obedience to a warrant issued under section 2 of the [1985 c. 56.] Interception of Communications Act 1985, any information relating to the obtaining of information by reason of any such interception and any document or other article which is or has been used or held for use in, or has been obtained by reason of, any such interception; and

(b) any information obtained by reason of action authorised by a warrant issued under section 3 of the [1989 c. 5.] Security Service Act 1989, any information relating to the obtaining of information by reason of any such action and any document or other article which is or has been used or held for use in, or has been obtained by reason of, any such action.

(4) It is a defence for a person charged with an offence under this section in respect of a disclosure falling within subsection (2)(a) above to prove that at the time of the alleged offence he did not know, and had no reasonable cause to believe, that the disclosure would have any of the effects there mentioned.

(5) It is a defence for a person charged with an offence under this section in respect of any other disclosure to prove that at the time of the alleged offence he did not know, and had no reasonable cause to believe, that the information, document or article in question was information or a document or article to which this section applies.

(6) In this section “legal custody” includes detention in pursuance of any enactment or any instrument made under an enactment.