Britain is appealing a court ruling that ordered the government to release documents relating to the alleged torture of a former Guantanamo Bay detainee.
Britain's High Court had said the government should release information on Binyam Mohamed, who claims he was tortured in Pakistan and Morocco.
Mohamed claims British intelligence material will support his claims, proving Britain was complicit in his torture.
Foreign Secretary David Miliband has argued that releasing the information would harm national security. Two High Court judges have said Miliband's argument isn't valid and the documents should be released in the public interest.
The case at the Court of Appeal is being heard Monday.