Information is exempt information if its disclosure under this Act would, or would be likely to, prejudice—
the defence of the British Islands or of any colony, or
the capability, effectiveness or security of any relevant forces.
In subsection (1)(b) "relevant forces" means—
the armed forces of the Crown, and
any forces co-operating with those forces,
or any part of any of those forces.
The duty to confirm or deny does not arise if, or to the extent that, compliance with section 1(1)(a) would, or would be likely to, prejudice any of the matters mentioned in subsection (1).