Official Secrets Act 1989

2 Defence

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

(2) For the purposes of subsection (1) above a disclosure is damaging if—

(a) it damages the capability of, or of any part of, the armed forces of the Crown to carry out their tasks or leads to loss of life or injury to members of those forces or serious damage to the equipment or installations of those forces; or

(b) otherwise than as mentioned in paragraph (a) above, it endangers the interests of the United Kingdom abroad, seriously obstructs the promotion or protection by the United Kingdom of those interests or endangers the safety of British citizens abroad; or

(c) it is of information or of a document or article which is such that its unauthorised disclosure would be likely to have any of those effects.

(3) It is a defence for a person charged with an offence under this section 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 related to defence or that its disclosure would be damaging within the meaning of subsection (1) above.

(4) In this section “defence” means—

(a) the size, shape, organisation, logistics, order of battle, deployment, operations, state of readiness and training of the armed forces of the Crown;

(b) the weapons, stores or other equipment of those forces and the invention, development, production and operation of such equipment and research relating to it;

(c) defence policy and strategy and military planning and intelligence;

(d) plans and measures for the maintenance of essential supplies and services that are or would be needed in time of war.